# Voltage controlled relay

Discussion in 'General Electronics Chat' started by rtm038, Nov 7, 2009.

1. ### rtm038 Thread Starter New Member

Oct 18, 2009
2
0
I'm looking for a simple circuit that will turn a standard Bosch automotive relay "On" at 10 volts and "Off" at 10 volts. This relay will be used to control (2) other relays in my truck, which has a 12+vdc electrical system. The approximate specs on the Bosch relay are: Pull-in voltage= 8 volts; Drop-out voltage= 1 to 5 volts; Coil resistance= 0.160 amps (75 ohms). Any help would be appreciated.

Ryan

2. ### mkbutan AAC Fanatic!

Sep 30, 2008
277
16
Bosch automotive relay "On" at 10 volts and "Off" at 10 volts.
Bosch relay are: Pull-in voltage= 8 volts;
i did nit understand the concept of 10V & 08V

3. ### bertus Administrator

Apr 5, 2008
19,170
3,836
Hello,

You could make a voltage comparator that switches round 10 volts.
This comparator could switch the relays.

Greetings,
Bertus

4. ### SgtWookie Expert

Jul 17, 2007
22,199
1,801
Hello Ryan,
I'm afraid that I'm not quite understanding your stated requirement.
Your threshold for both "on" and "off" is 10v.
Did you mean that for any voltage over 10v, you want the relay 'on', and any voltage under 10v you want the relay 'off'?

Or did you mean that the first time a level of 10v is detected the relay turns 'on', and the next time it goes 'off'?

Or did you mean something else entirely?

I am also curious about the 10v threshold; why that particular voltage?

If you are attempting to disengage a system before the battery is fully discharged, please be aware that a lead-acid battery with a core temperature of 25°C/77°F is considered fully discharged when the battery voltage is 10.4v; and allowing an automotive battery to become so discharged is very hard on it.

OK, it would be most helpful if you would describe as best you can exactly what you are attempting to do with this single relay controlling the two other relays.

It's very helpful to have the relay specifications; glad you included them.

Please describe the project in more detail, as best you can, starting with an overall concept statement; something like "I want to make sure my fog lamps are turned off before my battery goes dead". The more complete your information is, the more quickly we can help you successfully complete your project.