Building a relay board?

surftheearth

I am very new to electronics and have jumped in head first. I am working on a project to build a relay board which will control several 12v device on my boat. The challenge I am having is I am trying to determine when a pump turns on, start a timer, and shut it down if it runs pass a specific time.

I thought I might be able to do it by using get voltage but the pump always has voltage. Is it possible to detect current? Are there any projects online which have done a similar thing?

Any advice is appreciated.

Marc

Chet

You can use an opto isolator to determine when the pump is running. You can put a resistor in series with the Opto isolator to limit the current to the input to the O/I. Using a pullup resitor between the collector and the 5 v of the controller (SX or Stamp) and ground the emitter. Read the logic level at the collector to determine if the pump is running. If it is, the collector will give a low logic level. If off, the collector will be logic 1.
In the supply going to the pump, you need to install a N/C relay. That way the pump can function using its normal controls. If you need to shut it off, you can have the SX/stamp energize the relay to open the circuit and interupt the power to the pump. There are several examples on the board for the relay switching.

You could go a different way and intercept the signal that turns on the pump and have the SX/stamp do the control and have it limit the time the pump is on. The difference in the approach is in the first system the present wiring is stock and if the SX/stamp malfunction ( which they normally do not) then the original system will continue to function.

Hope this helps


Chet