Relay Circuit Design

[drmac]

I have a relay circuit which uses 3 power relays to control two AC motors and one AC light load. The relays are switched through a 12V signal from a darlington array ic. The two motors are alternating one on, one off every three minutes and the light load is continuously on.

The problem I am having is that the relay controlling the light will unexpectedly turn off after about 10 minutes of cycling the motors. I have 100uF caps on the relay coil lines but the light relay still looses contact.

Any suggestion on where to start troubleshooting, power supply issue (30mA each through 7812 v-reg), capacitance, etc?

thanks

 

[nbucska]

send schematics

<nbucska@pcperipherals DOT com> subj: eng-tips

 

[jraef]

Does it come back on after dropping out? If not, how do you get it to start working again?

&quot;Venditori de oleum-vipera non vigere excordis populi&quot;

 

[nbucska]

have you found the problem?


<nbucska@pcperipherals DOT com> subj: eng-tips