I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDetail/ON-Semiconductor-Fairchild/LM555CN?qs=AFLC8Sm4xaX0SxPz974UPA==
High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

--
Jeff

Harry wrote:

I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

A search using the part number and the keyword 'datasheet' reveals
many hits. A random one reveals an absolute maximum I-out of +/- 100mA
but recommended operating conditions of output sink current 10mA and
output source current of 50mA. The significance of the recommended
operating conditions is that it may well prove difficult to produce a
reliable practical circuit using much higher currents, though you are
allowed to sink more if you can get everything else right, including
dissipation and circuit function. So I recommend not going much above
the recommended 10mA.


--

Roger Hayter

Roger Hayter wrote:
A search using the part number and the keyword 'datasheet' reveals
many hits. A random one reveals an absolute maximum I-out of +/- 100mA
but recommended operating conditions of output sink current 10mA and
output source current of 50mA. The significance of the recommended
operating conditions is that it may well prove difficult to produce a
reliable practical circuit using much higher currents, though you are
allowed to sink more if you can get everything else right, including
dissipation and circuit function. So I recommend not going much above
the recommended 10mA.

If the LED is a modern one, rather than a 1970s one from the junk box, 10mA
continuous is likely to be blindingly bright. So I wouldn't worry about
needing the maximum current if it's just an indicator. You could also
probably pulse the LED harder for a shorter length of time if needs be too.

Theo

Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN
?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

--

Roger Hayter

I thought you could get leds that did this already?
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
Harry Bloomfield; "Esq." wrote in
message ...
I'm making an LED flasher as an indicator, for use on a 12 to 15v supply.
Directly driving an LED using a TS555CN timer IC. around one second off
and a few milli-second on, just long enough to spot, so as to minimise
current consumption. LED will be between +ve and output, so sinking
current, but I'm struggling to track down data on how many milliamps this
IC can safely sink on the output pin. Anyone know?

Theo wrote:

Roger Hayter wrote:
A search using the part number and the keyword 'datasheet' reveals
many hits. A random one reveals an absolute maximum I-out of +/- 100mA
but recommended operating conditions of output sink current 10mA and
output source current of 50mA. The significance of the recommended
operating conditions is that it may well prove difficult to produce a
reliable practical circuit using much higher currents, though you are
allowed to sink more if you can get everything else right, including
dissipation and circuit function. So I recommend not going much above
the recommended 10mA.

If the LED is a modern one, rather than a 1970s one from the junk box, 10mA
continuous is likely to be blindingly bright. So I wouldn't worry about
needing the maximum current if it's just an indicator. You could also
probably pulse the LED harder for a shorter length of time if needs be too.

Theo

If it were really important to have a higher peak current for a very
short time than the device could sink then you could use a capacitor
which is then discharged more slowly by the active device. But of
course the more average power used the less the OP's design criterion of
low power is met.

--

Roger Hayter

If you want to sinc more, surely 1 transistor should be able to suffice.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Roger Hayter" wrote in message
...
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN
?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

--

Roger Hayter

On Wed, 15 Jul 2020 22:23:08 +0100, Brian Gaff \(Sofa\) wrote:

I thought you could get leds that did this already?

There are but they tend to wink rather than a brief pulse flash that
the OP wants.

There is (was?) a dedicated LED flasher chip that used a charge pump
and capacitor to very effciently produce a bright pulsed LED. LM3909?

Note that's a "bright pulsed" mid 90's LED. A modern LED will be
extremely bright...

--
Cheers
Dave.

Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as to
minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

Use a bipolar transistor as a buffer ?

NPN

https://www.basic4mcu.com/data/file/....thumbnail.gif

PNP

https://www.eleccircuit.com/wp-conte...-by-ic-555.jpg

Circuit diagrams of this quality, redo your Hfe
and/or bias calcs. Today, there's hardly a situation
where I'd use a 2N3055, but at one time, I used
to drool at the chance to own one. The Hfe is kinda
low on those. Like driving a nail with a dull hammer.

Also, consider whether the result "inverts" or not,
and adjust your 555 design accordingly.

Another way to do this, is with a CD4538, with the
two units tied tip to tail. CD4000 series are
current limited in behavior, and sink or source
10mA on a good day. Definitely needs a bipolar
buffer. These are flexible enough, you can make
any waveform you want, with free Q and Qbar outputs
for a free inversion.

(This is a PDF file, add a file extension.)

https://www.uni-kl.de/elektronik-lager/418169

Page 6 here, gives an idea how to emulate a 555
using the two monostables in a 4538. You have
more options with stuff like this.

Fairchild Semiconductor Application Note 138 May 1975
"Using the CMOS Dual Monostable Multivibrator"

https://www.eeweb.com/app-notes/download/1543

Yes, not guaranteed to start or some such. Look
at the logic table carefully, when selecting
an input method, to make sure you've covered
that off.

I'd probably just grab a 2N2222 or similar from
the bin, for a start at a buffer.

And with the efficiency of modern LEDs, you might
be surprised how far 10mA goes. With a lens, such
a LED could be annoying.

Paul

On 15/07/2020 23:59, Paul wrote:

And with the efficiency of modern LEDs, you might
be surprised how far 10mA goes. With a lens, such
a LED could be annoying.

I have some "high efficiency" (ultra bright) LEDs running at just under
100uA and they are bright enough to be seen on an overcast day from 5+
metres away. These 5mm LEDS are specified at around 15000mcd brightness
at 20mA but with much reduced brightness at my operating 100uA.
I'm running two LEDs continuously from 4 off AAA alkaline batteries
which last 3 to 4 months before require changing.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

alan_m wrote:
On 15/07/2020 23:59, Paul wrote:

And with the efficiency of modern LEDs, you might
be surprised how far 10mA goes. With a lens, such
a LED could be annoying.

I have some "high efficiency" (ultra bright) LEDs running at just under
100uA and they are bright enough to be seen on an overcast day from 5+
metres away. These 5mm LEDS are specified at around 15000mcd brightness
at 20mA but with much reduced brightness at my operating 100uA.
I'm running two LEDs continuously from 4 off AAA alkaline batteries
which last 3 to 4 months before require changing.

If the OP has 15V to work with, the series resistor wastes
most of the energy.

You could put five 2.5V white LEDs in series, for 12.5V drop.
Leaving only 2.5V for the dropping resistor and the Vcesat.
And then get five times the light. Like, point the LEDs in
different directions so you can see the indicator from
more orientations.

An opportunity-rich project, suitable for breadboard first.

My first 555 project, was adding two yellow LEDs to a
frisbee, so you could throw the frisbee at night.

Paul

Roger Hayter expressed precisely :
So I recommend not going much above
the recommended 10mA.

Thanks, 10mA will cover it...

It is to be part of my new car battery maintenance regime. My old
regime was one of plugging my (not regularly enough used car), into a
smart charger once per month, to bring it to a full charge. My smart
chargers need a button to be pressed, after connecting, to begin the
charging. That requires some manual intervention, plus remembering to
do it. It can sit there for longer than a month, unused, especially so
in winter.
I don't like the idea of having batteries constantly on a maintenance
charger, I have had batteries ruined by them before.

The car's discharge due to its electronics is 20mA when parked. So I
have been trying to devise a 'fit and forget' system....

I had adapted the smart charger so it clips onto large terminals on a
roof beam in the garage, from the terminals there is a flex with a
lighter plug, which I can plug into the car to charge it. Once plugged
in, pressing the button on the smart charger, would confirm a good
connection has been made with the car, via the lighter socket.

I have decided a daily charge regime might be better. I have powered a
dumb 8amp voltage limited charger, via a time clock, so it comes on for
just 15 minutes per day. The dumb charger discharges 5mA whilst not
mains powered, its way to confirm it has the correct polarity. Charger
will not attempt to charge, unless it sees the correct polarity and
voltage from the battery.

Problem - When plugging in the ciggy lighter socket, ciggy lighter
sockets might not make a definite connection. The 555 and LED connected
to the terminals on the roof beam, will confirm I have made a good
connection and I can subsequently also check it at a glance, when I am
in my garage workshop.

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN
?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDetail/STMicroelectronics/TS555CN?qs=%2Fha2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdn J6tImk%3D
is the correct device. That states the 50/-10mA output as you noted. Any
idea why it should say the Power Dissipation is 1250mW? That figure
doesn't appear in the data sheet pdf link on the webpage.

--
Jeff

On 16/07/2020 08:49, Jeff Layman wrote:
On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN

?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current:Â*Â*Â*Â*Â* 50 mA
Low Level Output Current:Â*Â*Â*Â* - 200 mA
Pd - Power Dissipation:Â*Â*Â*Â*Â*Â* 600 mW

They're not the same.Â* The TS555CN is a CMOS low current device.Â* See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDetail/STMicroelectronics/TS555CN?qs=%2Fha2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdn J6tImk%3D

is the correct device. That states the 50/-10mA output as you noted. Any
idea why it should say the Power Dissipation is 1250mW? That figure
doesn't appear in the data sheet pdf link on the webpage.

anyone who puts 1,25W through a DIL 8 pin package is in for some magic
smoke. 125mW is more likely

--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

Jeff Layman wrote:
On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN

?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDetail/STMicroelectronics/TS555CN?qs=%2Fha2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdn J6tImk%3D

is the correct device. That states the 50/-10mA output as you noted. Any
idea why it should say the Power Dissipation is 1250mW? That figure
doesn't appear in the data sheet pdf link on the webpage.


Supply current max 250uA times VCC=5V gives 1250 uW (page 9).

Maybe the units got screwed up.

1.25mW is pretty good.

Paul

Jeff Layman wrote:

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN
?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta...S555CN?qs=%2Fh
a2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D is the correct device. That
states the 50/-10mA output as you noted. Any idea why it should say the
Power Dissipation is 1250mW? That figure doesn't appear in the data sheet
pdf link on the webpage.

No idea. Although you can derive a figure from the thermal
characteristics, maximum operating temperature and an arbitrary
assumption about case temperature.

--

Roger Hayter

The Natural Philosopher wrote:

On 16/07/2020 08:49, Jeff Layman wrote:
On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN

?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta.../TS555CN?qs=%2
Fha2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D

is the correct device. That states the 50/-10mA output as you noted. Any
idea why it should say the Power Dissipation is 1250mW? That figure
doesn't appear in the data sheet pdf link on the webpage.

anyone who puts 1,25W through a DIL 8 pin package is in for some magic
smoke. 125mW is more likely

Maximum dissipation is typically a marketing figure, based on totally
unrealistic heat sink arrangements. With power devices they tend also
to give you a realistic figure based on credible heatsinks. But with a
CMOS device generally you are using it to save power. (Except for high
frequency use where you would still not be able to approach the headline
maximum dissipation but it might get quite hot.)



--

Roger Hayter

On 16/07/2020 10:33, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN
?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta...S555CN?qs=%2Fh
a2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D is the correct device. That
states the 50/-10mA output as you noted. Any idea why it should say the
Power Dissipation is 1250mW? That figure doesn't appear in the data sheet
pdf link on the webpage.

No idea. Although you can derive a figure from the thermal
characteristics, maximum operating temperature and an arbitrary
assumption about case temperature.

Actually you cant.

I tried and at best I came up with 1W on a very good thermally
conductive PCB, for 25C ambient.

And as experienced designer in these matters no kit that didn't expect
to get to around 50C inside a cease ever survived.

So you have at best 100C to play with, for a 150C junction temperature
and the spec says IIRC 125C per watt - so around 800mW at the most.
But its a pretty useless spec anyway since its unlikely that a chip that
can only source 50mA at 5V - 250mW - into an external load, is going to
be able to dissipate 750mW unless its output is completely shorted.




--
€œIt is hard to imagine a more stupid decision or more dangerous way of
making decisions than by putting those decisions in the hands of people
who pay no price for being wrong.€�

Thomas Sowell

On 16/07/2020 10:57, Roger Hayter wrote:
The Natural Philosopher wrote:

On 16/07/2020 08:49, Jeff Layman wrote:
On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN

?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta.../TS555CN?qs=%2
Fha2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D

is the correct device. That states the 50/-10mA output as you noted. Any
idea why it should say the Power Dissipation is 1250mW? That figure
doesn't appear in the data sheet pdf link on the webpage.

anyone who puts 1,25W through a DIL 8 pin package is in for some magic
smoke. 125mW is more likely

Maximum dissipation is typically a marketing figure, based on totally
unrealistic heat sink arrangements. With power devices they tend also
to give you a realistic figure based on credible heatsinks. But with a
CMOS device generally you are using it to save power. (Except for high
frequency use where you would still not be able to approach the headline
maximum dissipation but it might get quite hot.)



Actually they normally give two totally hopeless figures - maximum
dissipation on an 'infinite heatsink' and maximum dissipation in free
air, both at 25C.


To work out actual permissible dissipation you need to know the thermal
resistance of the heatsink - or PCB if that is what its mounted on - and
the likely ambient temperature.

During my time designing power amps in Africa, a black heatsink in the
sun could reach 80C before even being switched on...and ambient temps in
discothèques were often up in the sweaty 40s.

In the end we simply built them and raised the thermal cutout switch
point until they didnt pack up in normal use or die from heat either.


--
€œIt is dangerous to be right in matters on which the established
authorities are wrong.€�

ۥ Voltaire, The Age of Louis XIV

The Natural Philosopher wrote:

On 16/07/2020 10:33, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...r-Fairchild/LM
555CN ?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current:
50 mA Low Level Output Current: - 200 mA Pd - Power Dissipation:
600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta...s/TS555CN?qs=%
2Fh a2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D is the correct
device. That states the 50/-10mA output as you noted. Any idea why it
should say the Power Dissipation is 1250mW? That figure doesn't appear
in the data sheet pdf link on the webpage.

No idea. Although you can derive a figure from the thermal
characteristics, maximum operating temperature and an arbitrary
assumption about case temperature.

Actually you cant.

I tried and at best I came up with 1W on a very good thermally
conductive PCB, for 25C ambient.

And as experienced designer in these matters no kit that didn't expect
to get to around 50C inside a cease ever survived.

So you have at best 100C to play with, for a 150C junction temperature
and the spec says IIRC 125C per watt - so around 800mW at the most.
But its a pretty useless spec anyway since its unlikely that a chip that
can only source 50mA at 5V - 250mW - into an external load, is going to
be able to dissipate 750mW unless its output is completely shorted.

I didn't say it was a useful figure - like most marketing its only
purpose is to sound good. I just said you could derive it! How about
40degC/W junction to case thermal resistance, case temperature 70degC,
max junction temp 150degC? That gives you 2000mW. Nonsense, I agree.


--

Roger Hayter

On 16/07/2020 07:23, Harry Bloomfield wrote:


Problem - When plugging in the ciggy lighter socket, ciggy lighter
sockets might not make a definite connection. The 555 and LED connected
to the terminals on the roof beam, will confirm I have made a good
connection and I can subsequently also check it at a glance, when I am
in my garage workshop.


Modern cars call the ciggy lighter a 12V power supply and on some cars
it is disabled 10 to 15 minutes after the ignition is turned off.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

alan_m explained :
Modern cars call the ciggy lighter a 12V power supply and on some cars it is
disabled 10 to 15 minutes after the ignition is turned off.

I have a choice of one live all the time, two which go off with the
ignition.

On 16/07/2020 11:08, Roger Hayter wrote:
The Natural Philosopher wrote:

On 16/07/2020 10:33, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...r-Fairchild/LM
555CN ?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current:
50 mA Low Level Output Current: - 200 mA Pd - Power Dissipation:
600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta...s/TS555CN?qs=%
2Fh a2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D is the correct
device. That states the 50/-10mA output as you noted. Any idea why it
should say the Power Dissipation is 1250mW? That figure doesn't appear
in the data sheet pdf link on the webpage.

No idea. Although you can derive a figure from the thermal
characteristics, maximum operating temperature and an arbitrary
assumption about case temperature.

Actually you cant.

I tried and at best I came up with 1W on a very good thermally
conductive PCB, for 25C ambient.

And as experienced designer in these matters no kit that didn't expect
to get to around 50C inside a cease ever survived.

So you have at best 100C to play with, for a 150C junction temperature
and the spec says IIRC 125C per watt - so around 800mW at the most.
But its a pretty useless spec anyway since its unlikely that a chip that
can only source 50mA at 5V - 250mW - into an external load, is going to
be able to dissipate 750mW unless its output is completely shorted.

I didn't say it was a useful figure - like most marketing its only
purpose is to sound good. I just said you could derive it! How about
40degC/W junction to case thermal resistance, case temperature 70degC,
max junction temp 150degC? That gives you 2000mW. Nonsense, I agree.




But that is not the quoted junction to case thermal resistance. It SAYS
it's 125C/W.

In the specs....



--
Its easier to fool people than to convince them that they have been fooled.
Mark Twain

The Natural Philosopher wrote:

On 16/07/2020 11:08, Roger Hayter wrote:
The Natural Philosopher wrote:

On 16/07/2020 10:33, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote: I'm making an LED
flasher as an indicator, for use on a 12 to 15v supply. Directly
driving an LED using a TS555CN timer IC. around one second off and
a few milli-second on, just long enough to spot, so as to minimise
current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...tor-Fairchild/
LM 555CN ?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current:
50 mA Low Level Output Current: - 200 mA Pd - Power
Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device.
See Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta...ics/TS555CN?qs
=% 2Fh a2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D is the correct
device. That states the 50/-10mA output as you noted. Any idea why it
should say the Power Dissipation is 1250mW? That figure doesn't
appear in the data sheet pdf link on the webpage.

No idea. Although you can derive a figure from the thermal
characteristics, maximum operating temperature and an arbitrary
assumption about case temperature.

Actually you cant.

I tried and at best I came up with 1W on a very good thermally
conductive PCB, for 25C ambient.

And as experienced designer in these matters no kit that didn't expect
to get to around 50C inside a cease ever survived.

So you have at best 100C to play with, for a 150C junction temperature
and the spec says IIRC 125C per watt - so around 800mW at the most.
But its a pretty useless spec anyway since its unlikely that a chip that
can only source 50mA at 5V - 250mW - into an external load, is going to
be able to dissipate 750mW unless its output is completely shorted.

I didn't say it was a useful figure - like most marketing its only
purpose is to sound good. I just said you could derive it! How about
40degC/W junction to case thermal resistance, case temperature 70degC,
max junction temp 150degC? That gives you 2000mW. Nonsense, I agree.




But that is not the quoted junction to case thermal resistance. It SAYS
it's 125C/W.

In the specs....

AIR it is 125degC/W junction to ambient (typical PCB) and 40degC/W
junction to case.


--

Roger Hayter

In article ,
Harry Bloomfield wrote:
I don't like the idea of having batteries constantly on a maintenance
charger, I have had batteries ruined by them before.

The cheap Lidl one seems to be perfectly happy to be left in maintenance
mode forever. And the battery too.

An older basic trickle charger might well cook the battery.

Given how cheap the Lidl ones are, why not build one into the car? No need
for iffy fag lighter etc connections then. Mine is wired across the
battery (via a fuse). With a weatherproof mains inlet under the bumper.

Just set a reminder on your computer to switch it on once every three
weeks or whatever, if you don't like leaving it on.

--
*Is there another word for synonym?

Dave Plowman London SW
To e-mail, change noise into sound.

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote:
I'm making an LED flasher as an indicator, for use on a 12 to 15v
supply. Directly driving an LED using a TS555CN timer IC. around one
second off and a few milli-second on, just long enough to spot, so as
to minimise current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...rchild/LM555CN
?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current: 50 mA
Low Level Output Current: - 200 mA
Pd - Power Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device. See
Mouser's entry for the right part or my post above.

ISTR +/-100mA at 12-15V and about 500mW max dissipation see eg.

https://www.st.com/resource/en/datasheet/ts555.pdf

Page 3/19

There is a very old school discrete LED flasher circuit that slowly
charges up a capacitor through a large resistor and then discharges it
quickly through the LED (or flashing LEDs for that matter). Both methods
would use less power.

That said my late 70's mains Xmas lights flasher used a CMOS555 and the
9v battery in it lasted 3-4 years continuously running (rather longer
than you would predict from the PP9 0.5Ah battery capacity and the
nominal 50uA standby current ~0.5Ah/year consumption). It helps that the
thing will continue to work right down to a terminal voltage of 2v.

Beware of battery leakage if you push things too far though.

--
Regards,
Martin Brown

Dave Plowman (News) used his keyboard to write :
Given how cheap the Lidl ones are, why not build one into the car? No need
for iffy fag lighter etc connections then. Mine is wired across the
battery (via a fuse). With a weatherproof mains inlet under the bumper.

Just set a reminder on your computer to switch it on once every three
weeks or whatever, if you don't like leaving it on.

Problem - If power is lost, the Lidl unit stops charging until I notice
it. Using my old charging regime, the battery would be discharging for
a month, then brought up to full charge.

Building the Lidl in, would probably need it to be under the bonnet, or
in the cab, opening the bonnet to run 240v in versus just bring the 12v
ciggy lead in through the open car door. Via the car door, it reminds
me to disconnect, before driving off.

My only issue with my dumb charger on a time clock, is confirming the
siggy lighter plug has made good contact, because the dumb charger when
off, doesn't confirm it is seeing 12v from the car. Hence adding a low
current LED flasher.

On Thursday, 16 July 2020 16:42:21 UTC+1, wrote:
Dave Plowman (News) used his keyboard to write :
Given how cheap the Lidl ones are, why not build one into the car? No need
for iffy fag lighter etc connections then. Mine is wired across the
battery (via a fuse). With a weatherproof mains inlet under the bumper.

Just set a reminder on your computer to switch it on once every three
weeks or whatever, if you don't like leaving it on.

Problem - If power is lost, the Lidl unit stops charging until I notice
it. Using my old charging regime, the battery would be discharging for
a month, then brought up to full charge.

Building the Lidl in, would probably need it to be under the bonnet, or
in the cab, opening the bonnet to run 240v in versus just bring the 12v
ciggy lead in through the open car door. Via the car door, it reminds
me to disconnect, before driving off.

My only issue with my dumb charger on a time clock, is confirming the
siggy lighter plug has made good contact, because the dumb charger when
off, doesn't confirm it is seeing 12v from the car. Hence adding a low
current LED flasher.

You're making life difficult. Some LEDs are viewable with microamps of current. Forget the 555.


NT

In article ,
Harry Bloomfield wrote:
Dave Plowman (News) used his keyboard to write :
Given how cheap the Lidl ones are, why not build one into the car? No
need for iffy fag lighter etc connections then. Mine is wired across
the battery (via a fuse). With a weatherproof mains inlet under the
bumper.

Just set a reminder on your computer to switch it on once every three
weeks or whatever, if you don't like leaving it on.

Problem - If power is lost, the Lidl unit stops charging until I notice
it. Using my old charging regime, the battery would be discharging for
a month, then brought up to full charge.

Do you really have power cuts that often?

Building the Lidl in, would probably need it to be under the bonnet, or
in the cab, opening the bonnet to run 240v in versus just bring the 12v
ciggy lead in through the open car door. Via the car door, it reminds
me to disconnect, before driving off.

In the boot? Assuming there is 24 hour power there.

As regards mains, you could do the same as fire engines. Make sure the
connector would pull out if you drove off. ;-)

My only issue with my dumb charger on a time clock, is confirming the
siggy lighter plug has made good contact, because the dumb charger when
off, doesn't confirm it is seeing 12v from the car. Hence adding a low
current LED flasher.

I'd say the fag lighter connection the weak link in the chain.

--
*He who dies with the most toys is, nonetheless, dead.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) explained on 16/07/2020 :
In article ,
Harry Bloomfield wrote:
Dave Plowman (News) used his keyboard to write :

Do you really have power cuts that often?

No, but I do sometimes trip the RCD for my garage workshop supply.


In the boot? Assuming there is 24 hour power there.

Probably the worst possible place and easiest to forget it.

As regards mains, you could do the same as fire engines. Make sure the
connector would pull out if you drove off. ;-)

My ciggy lighter socket is fine, just needs something to confirm a
connection has been made.


My only issue with my dumb charger on a time clock, is confirming the
siggy lighter plug has made good contact, because the dumb charger when
off, doesn't confirm it is seeing 12v from the car. Hence adding a low
current LED flasher.

I'd say the fag lighter connection the weak link in the chain.

On 16/07/2020 14:00, Roger Hayter wrote:
The Natural Philosopher wrote:

On 16/07/2020 11:08, Roger Hayter wrote:
The Natural Philosopher wrote:

On 16/07/2020 10:33, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 22:10, Roger Hayter wrote:
Jeff Layman wrote:

On 15/07/2020 21:17, Harry Bloomfield wrote: I'm making an LED
flasher as an indicator, for use on a 12 to 15v supply. Directly
driving an LED using a TS555CN timer IC. around one second off and
a few milli-second on, just long enough to spot, so as to minimise
current consumption. LED will be between +ve and output, so
sinking current, but I'm struggling to track down data on how many
milliamps this IC can safely sink on the output pin. Anyone know?

If he LM555CN is the same, then according to
https://www.mouser.co.uk/ProductDeta...tor-Fairchild/
LM 555CN ?qs=AFLC8Sm4xaX0SxPz974UPA== High Level Output Current:
50 mA Low Level Output Current: - 200 mA Pd - Power
Dissipation: 600 mW

They're not the same. The TS555CN is a CMOS low current device.
See Mouser's entry for the right part or my post above.

I see that
https://www.mouser.co.uk/ProductDeta...ics/TS555CN?qs
=% 2Fh a2pyFadugwGJBCbSC1QHhRZHNAKyQRMeZdnJ6tImk%3D is the correct
device. That states the 50/-10mA output as you noted. Any idea why it
should say the Power Dissipation is 1250mW? That figure doesn't
appear in the data sheet pdf link on the webpage.

No idea. Although you can derive a figure from the thermal
characteristics, maximum operating temperature and an arbitrary
assumption about case temperature.

Actually you cant.

I tried and at best I came up with 1W on a very good thermally
conductive PCB, for 25C ambient.

And as experienced designer in these matters no kit that didn't expect
to get to around 50C inside a cease ever survived.

So you have at best 100C to play with, for a 150C junction temperature
and the spec says IIRC 125C per watt - so around 800mW at the most.
But its a pretty useless spec anyway since its unlikely that a chip that
can only source 50mA at 5V - 250mW - into an external load, is going to
be able to dissipate 750mW unless its output is completely shorted.

I didn't say it was a useful figure - like most marketing its only
purpose is to sound good. I just said you could derive it! How about
40degC/W junction to case thermal resistance, case temperature 70degC,
max junction temp 150degC? That gives you 2000mW. Nonsense, I agree.




But that is not the quoted junction to case thermal resistance. It SAYS
it's 125C/W.

In the specs....

AIR it is 125degC/W junction to ambient (typical PCB) and 40degC/W
junction to case.


yeah. realised that ten minutes after I posted it That's the old
'infinite heatsink' case. That told you you could get a 2N3055 to
dissipate 100W...

....or 5W in free air..The numbers DO have meaning if you know the
ambient and the thermal conductivity of the heat sink.

But a DIL chip on a PCB is close to free air, and anyone who assumes
ambient in electronics kit is 25C is in for a shock


--
Labour - a bunch of rich people convincing poor people to vote for rich
people by telling poor people that "other" rich people are the reason
they are poor.

Peter Thompson

On Wed, 15 Jul 2020 22:25:38 +0100, Brian Gaff \(Sofa\) wrote:

If you want to sinc more, surely 1 transistor should be able to suffice.
Brian

I
saw a 2n3055 somewhere.....my goodness me