On Tue, 13 Oct 2020 20:34:04 -0400, Paul
wrote:
snip
Assumed doorbell circuit. Arrows go to extension circuit.
------+------- solenoid -------+
| | +
\ x ----- 6V
\ ---
x | -
| |
------+------------------------+
Spot on.
+-------------
|
RLED (6-2)V / 10mA = 390 ohms 1/8th watt
| or larger
+-----+ Limits current while LED runs.
+ | | Limits charging current too though.
----- --- Use two resistors, one per diode, to adjust this.
1N4001 \ / ^
v / \ LED Yellow 2.0V LED
--- -----
| | +
+-----+
+ |
--- 2200uF (salt to taste, RLED*C tau)
--- C
|
+-------------
Nice thinking Paul. The 'clever' thing about that (assuming they are
looking for the LED etc) is that it could all be in / just behind the
bell-push (that is on the uPVC door frame).
If the cap isn't recharging fast enough for taste
(LED doesn't work when nervous nelly does a drum
solo on the button)...
'Nervous Nelly' weg
This will allow the cap to
recover between staccato button presses, a little bit.
I'm not bothered about that / them Paul. TBF, most people generally
either press it once 'normally' (press - release) or go for the 'I'll
ring it longer' but then I just get the 'Ding ............. dong'. ;-)
The lower limit on resistor value, is 1N4001 current
rating, and you can use a larger diode if desired.
I might have to be careful that too small a resistor causes the
solenoid to hang or not allow the 'dong' if it doesn't release cleanly
as it's re-charging the cap?
I just happen to have a pack of 1n400x sitting around,
so it's the first number that comes to mind.
I have a roll of them as well. ;-)
They're
pretty cheap if not bought at Radio Shack.
Quite! Buying two diodes from RS was normally the same price as 100 at
my local electronics suppliers (all now long gone though). ;-(
+-------------
|
6.2 RCAP Limits diode current flow, use larger diode if desired...
Ohms | Recharges cap for next pulse, more quickly.
+-----+
| |
| RLED (6-2)V / 10mA = 390 ohms 1/8th watt
| | or larger
| | Limits current while LED runs.
+ | |
----- --- Diode prevents 5V from appearing
1N4001 \ / ^ across the reversed yellow LED. Only
v / \ LED Yellow 2V indicator LEDs allow a PIV like this.
--- ----- Power LEDs are less tolerant on PIV.
| | +
+-----+
+ |
--- 2200uF (salt to taste, RLED*C tau)
--- C Grab any old cap from the electrolytics box, and test :-)
| You'll be breadboarding this circuit before buildup.
+------------- to get the aesthetics right.
If you make the RLED a lower value, like say 220 ohm,
to get more current through the LED, then the cap
value rises to give the same time constant as before.
OK.
If you use back-to-back LEDs, then the button release
gets a bit of color too. You want LEDs with similar
Vf, so that the current flow levels aren't too much
different during charge/discharge of the cap. Yellow
and red would be good. Throwing blue into the circuit
less so (blue is used in white LEDs too). The cap will not
charge quickly enough if you do this (you would be using
the first circuit, not the second), so having two colors
to show, means the quick-button-pressers that play a drum
solo on the button, don't get good lighting on subsequent
tries.
Noted.
The Vf actually follows Plancks constant, so the
forward voltage isn't as "arbitrary" as it looks here (table).
Blue, which is up the higher energy end of the band,
has the higher Vf. You would then predict infrared
LEDs, would be a lot lower Vf, without having to look
it up. If I was doing two colors, red and green or red and
yellow might be decent mixes. Blue and infrared would be
too far apart to share a single resistor value.
Noted.
https://www.circuitbread.com/ee-faq/...different-leds
The only question then, is whether leakage in the switch,
or leakage in the capacitor, could lead to the batteries
discharging to nothing, one of the cells reverse bias,
juice ends up in the battery bay, eats the contacts
in the battery bay, and so on...
I don't think the switch would leak at all (unless it was wet)so it
would be down to the cap.
You could make the
capacitor out of a large number of ceramics, but maybe the
leakage would still not be exactly zero. The "large" ceramics
I bought on sale, they're a bit leaky.
I think it would all be a trade off between functionality (both
electronically and in RW outcome)and 'increased burden' on the system
/ batteries etc.
And doorbell switches are *the worst* switches on earth.
Agreed, certainly in refinement but then maybe they need to be like
that if they get wet / dirty?
They really put the effort into making awful ones
(no precious metals on the contacts).
;-)
Anyway, you can have fun playing with the concept
and whip something up.
Thanks ... and thanks very much for all your effort re diagrams and
explanations etc. You are very kind. ;-)
If you don't like LEDs,
you could substitute something else, subject to the
available voltage and current. And also, whether
reverse PIV (0.7V via the 1N4001) is OK or not.
I like relays and you can get some fairly small ones these days. They
are pretty durable and generally last for a fair few operations,
especially if driven and rated correctly.
I think I agree with some of the other replies suggesting an audio
confirmation might be more of a 'catch all' solution, re a small
mechanical buzzer mounted behind the bell-push on the inside of the
door frame. If I could get some charge in a cap to act as a remote PSU
and use your idea (probably with a second cap) to activate a small
relay that then self latches, powering the buzzer from the PSU cap?
I'd need to draw it out to see if / how it might work.
I will try the LED solution on the bench though after measuring the
current through the doorbell.
One of the reasons for me putting the 1N4001 in the
circuit, was as a PIV protection feature, so the
PIV (peak-inverse-volts) situation would not be quite as bad.
Yes, that was mentioned elsewhere etc. One advantage of the nasty /
crude bell-push is it's pretty resilient to such things. ;-)
Thanks again Paul.
Cheers, T i m