Hi all,

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

My thought is to put some sort of resistor in line on the main battery
feed so I can slowly reduce the voltage to a point where it trips the
recharge indicator. A voltmeter after the resistor would allow me to
monitor the voltage level where the recharge indicator is activated.

I am not an electronics guru (obviously) so something "off the shelf"
would be great.
Maybe some type of adjustable resistor? Any ideas?

Thanks.

wrote in message
ps.com...
Hi all,

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

My thought is to put some sort of resistor in line on the main battery
feed so I can slowly reduce the voltage to a point where it trips the
recharge indicator. A voltmeter after the resistor would allow me to
monitor the voltage level where the recharge indicator is activated.

I am not an electronics guru (obviously) so something "off the shelf"
would be great.
Maybe some type of adjustable resistor? Any ideas?

Thanks.


The easiest way to do that would be to beg or borrow an adjustable power supply.
Substitute the battery with the power supply.
Set the power supply to the nominal battery voltage, connect the voltmeter to
the power supply output, then slowly adjust the power supply output voltage
until the recharge indicator turns on.

Cheers...
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

How about using two 12V car bulb (current drain can be control by selection
of watts) and connected them in series (making up a 24V load). Then connect
it at the battery and wait for the voltage drop.


"DaveM" ¼¶¼g©ó¶l¥ó·s»D:LpqdnV5VeuzcCg7bnZ2dnUVZ_hudnZ2d@co mcast.com...
wrote in message
ps.com...
Hi all,

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

My thought is to put some sort of resistor in line on the main battery
feed so I can slowly reduce the voltage to a point where it trips the
recharge indicator. A voltmeter after the resistor would allow me to
monitor the voltage level where the recharge indicator is activated.

I am not an electronics guru (obviously) so something "off the shelf"
would be great.
Maybe some type of adjustable resistor? Any ideas?

Thanks.


The easiest way to do that would be to beg or borrow an adjustable power
supply. Substitute the battery with the power supply.
Set the power supply to the nominal battery voltage, connect the voltmeter
to the power supply output, then slowly adjust the power supply output
voltage until the recharge indicator turns on.

Cheers...
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters
in the address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

Unfortunately, I don't have anyone to beg or borrow one from. I hoped
to just add the "adjuster" set up to an extra battery pack for future
testing use. Is there anything out there that i can put in line? If
anyone knows the proper terminology for what I need, I can try and
search for one.

Thanks again!


On Jul 10, 9:27 am, "DaveM" wrote:
wrote in message

ps.com...





Hi all,

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

My thought is to put some sort of resistor in line on the main battery
feed so I can slowly reduce the voltage to a point where it trips the
recharge indicator. A voltmeter after the resistor would allow me to
monitor the voltage level where the recharge indicator is activated.

I am not an electronics guru (obviously) so something "off the shelf"
would be great.
Maybe some type of adjustable resistor? Any ideas?

Thanks.

The easiest way to do that would be to beg or borrow an adjustable power supply.
Substitute the battery with the power supply.
Set the power supply to the nominal battery voltage, connect the voltmeter to
the power supply output, then slowly adjust the power supply output voltage
until the recharge indicator turns on.

Cheers...
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra- Hide quoted text -

- Show quoted text -

wrote in message
ps.com...
Hi all,

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

My thought is to put some sort of resistor in line on the main battery
feed so I can slowly reduce the voltage to a point where it trips the
recharge indicator. A voltmeter after the resistor would allow me to
monitor the voltage level where the recharge indicator is activated.

I am not an electronics guru (obviously) so something "off the shelf"
would be great.
Maybe some type of adjustable resistor? Any ideas?

Thanks.

If the draw is really around 600mA, then you're not going to do it with a
pot. As Dave suggested, the best way to do it would be with a variable PSU
subbed for the battery, but failing that, you could use 1 ohm resistors
inserted in series with the battery. Each one added in series will cause a
drop of about 0.6v (not quite true as the amount dropped depends on the
current draw, and as the volts drop, the draw will probably also drop as
well, but near enough to do what you want to do). Each resistor should be a
1 watt type, which will still get pretty warm. If you wanted to use a higher
wattage, that's fine. If it does what you want, and you want to be able to
use it again in the future, you could just wire the resistors to a single
pole rotary switch. If you want to go a bit 'finer' with each step, you
could use 0.47 ohm resistors to give about 0.3v per step, or 0.22 ohm for
half that again. Obviously, these are all approximate figures, but right
ball park for what you want, and not of any consequence how accurate anyway,
if you are going to have a voltmeter slung across the test. If that sounds
like what you need, and you don't know how to wire such a switch, mail me
direct.

Arfa

On Tue, 10 Jul 2007 07:05:44 -0700, put
finger to keyboard and composed:

Hi all,

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

My thought is to put some sort of resistor in line on the main battery
feed so I can slowly reduce the voltage to a point where it trips the
recharge indicator. A voltmeter after the resistor would allow me to
monitor the voltage level where the recharge indicator is activated.

I am not an electronics guru (obviously) so something "off the shelf"
would be great.
Maybe some type of adjustable resistor? Any ideas?

Thanks.

Make up a bank of series cells, eg 14 or 15 AA alkalines, or C or D
cells if you can justify the cost. Just do your testing quickly.
Otherwise try to disconnect the load section of your circuit and keep
the sensing section operating.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Jul 10, 7:05 am, wrote:

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

It's easy to run an adjustable voltage regulator (LM317) for this
purpose; two fixed resistors and one adjustable resistor, the LM317,
and a small capacitor (probably not required, but it's recommended)
will make a 18-23V regulator. Just power the regulator from the
battery, wiggle the pot 'til it measures 22VDC output, and draw
a red line there. Or do it right, put a 'too low' line at 21.3V and a
'too high' line at 22.6V.

Radio Shack should have all the parts.

The regulator can be inserted between a fully charged battery and
the unit-under-test. It's going to need some heatsinking on the
regulator (get an aluminum box for the project, and bolt the
regulator chip through the convenient hole).

I think the term is Rheostat. Please read the following link on the High
power type rheostat.

http://en.wikipedia.org/wiki/Rheostat

Hope it is useful.


"whit3rd"
roups.com...
On Jul 10, 7:05 am, wrote:

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

It's easy to run an adjustable voltage regulator (LM317) for this
purpose; two fixed resistors and one adjustable resistor, the LM317,
and a small capacitor (probably not required, but it's recommended)
will make a 18-23V regulator. Just power the regulator from the
battery, wiggle the pot 'til it measures 22VDC output, and draw
a red line there. Or do it right, put a 'too low' line at 21.3V and a
'too high' line at 22.6V.

Radio Shack should have all the parts.

The regulator can be inserted between a fully charged battery and
the unit-under-test. It's going to need some heatsinking on the
regulator (get an aluminum box for the project, and bolt the
regulator chip through the convenient hole).

Power it up with 16 "C" or "D" batteries in series (16 x 1.5 = 24
volts), and wait for the voltage to drop. Buy the cheapie batteries
(zinc carbon, often labeled "super duty" or something equally
misleading), since they are less expensive and discharge quicker than
alkalines.

Bill

-------------------------------------------
wrote:
Hi all,

I need some help here.
I want to verify a voltage "trip" point on a board that operates on
battery supplied 24vdc.
The maximum draw is about 600MA

The board should change to "recharge required" at 22VDC

My thought is to put some sort of resistor in line on the main battery
feed so I can slowly reduce the voltage to a point where it trips the
recharge indicator. A voltmeter after the resistor would allow me to
monitor the voltage level where the recharge indicator is activated.

I am not an electronics guru (obviously) so something "off the shelf"
would be great.
Maybe some type of adjustable resistor? Any ideas?

Thanks.