Hi Guy's
I need a little help with a 12v system, I'm not that hot with electronics so any help or advice will be most welcome.
OK here goes
I have a water tank in my van the water comes from the tank to a 12v pump the pump is controlled by a 12v electronic controller and all works well.
I have added a heater to heat the water and this is were my problem began.
I added a relay between the 12v controller and the pump using the 12v supply, everything is working fine, the only trouble is I have to increase my water flow to activate the relay, the controller is just an expensive variable resistor, so to keep my water flow down I turn a knob on the controller and this has the affect of reducing the voltage on the relay.
These are the readings I have collected from my system.
12.36V across the main battery terminals
10.2V across the relay terminals with the pump running full speed
6.8V is the minimum power required to switch the relay (pump controller dialed to 3.5)
4.5V is what I have with the controller turned to 2 which is the minimum setting I would ever use.
So,.. I need a relay that will switch at 4.5V or below, but still be able to handle 10.2V -12v without burning out.
Failing the availability of a relay with this type of range to operate my boiler with, is there a power transistor or similar I could use to take the place of the relay.
I have drawn a diagram of what I mean in the hope it helps with my poor explanation.
**broken link removed**