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/5532/1...7612e531_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/7440/1...deb1394f_o.gif
And, the alarm system control panel powered up & beeped (almost) normally:
http://farm8.staticflickr.com/7440/1...e09daa9a_o.gif
With the battery in, or out, it gave the following error:
*ALL ON, SYSTEM TROUBLE*
http://farm4.staticflickr.com/3765/1...d907e787_o.gif
And, when I tried to read the error, it merely said:
*CALL FOR SERVICE*
http://farm4.staticflickr.com/3829/1...cb163704_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?)