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Re: Alarm system transformer + power supply (would both go bad at once?)



On Mon, 25 Nov 2013 20:50:39 -0500, tm wrote:

> It is a real simple circuit. There is an NPN transistor (Q1) that drives the
> relay. The black diode is across the relay coil to protect the transistor.
> The other diode is a zener in series with the 2.4 k resistor to the base of
> the transistor. When the battery voltage is above 9.x volts, the zener will
> conduct and turn on the transistor that will in turn operate the relay. The
> relay will make the connection from the red wire to the battery (W1) to the
> J2 terminal marked power. It will supply voltage to the alarm panel until
> the battery voltage drops below the zener diode conduction point.

Hi tm,

That was a FANTASTIC explanation!
You're one of the reasons why the USENET is so great!
Thank you very much for that detailed explanation.

I picked up an electrolytic cap, and I will replace it, and test the
battery-protection circuit out.

> Charge your battery for a while and see if it will light a simple tail light
> bulb. Measure the battery with the bulb connected and lit.

It failed this loaded test. So, now I know I have a bad battery and a
bad transformer.

Luckily, the *new* 16.5VAC transformer arrived.

It sure tested funny:
 http://farm6.staticflickr.com/5532/11078019855_b27612e531_o.gif

a) Secondary output = 20VAC
b) One side to ground = 3.5 Volts
c) The other side to ground = 1 Volt

Anyway, the moment I plugged that transformer in, the battery charging
circuit came to life at 13.6 Volts:
 http://farm8.staticflickr.com/7440/11078202723_a6deb1394f_o.gif

And, the alarm system control panel powered up & beeped (almost) normally:
 http://farm8.staticflickr.com/7440/11078202843_a0e09daa9a_o.gif

With the battery in, or out, it gave the following error:
 *ALL ON, SYSTEM TROUBLE*
 http://farm4.staticflickr.com/3765/11078125064_68d907e787_o.gif

And, when I tried to read the error, it merely said:
 *CALL FOR SERVICE*
 http://farm4.staticflickr.com/3829/11078125174_95cb163704_o.gif

I'm not sure how to get the actual service problem, but, I am pretty
sure it's the battery now that the new transformer is in place.

So, I'll google for a good source of batteries online.
(Any suggestions or are they all essentially the same?)



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