Timer circuit

Discussion in 'The Projects Forum' started by Larry Beach, Jul 22, 2010.

  1. Larry Beach

    Thread Starter New Member

    Jul 22, 2010
    Here is what I am trying to accomplish.

    We have a rental fleet of excavators that we mount Hydraulic hammers on. The chisel in these hammers needs to be lubricated with a special grease at a certain duration. I have wired in an electric (24VDC) greaser controlled by a pressure switch in the control system (ppc circuit) however the greaser runs continually when the hammer is activated and wastes a lot of grease. I purchased a timer relay and install it into that circuit. When energized it greases for about 2-3 seconds and then stops. When the circuit is re-energized it does it again. It is not ideal for this application for the following reasons.
    • When you are breaking thin concrete you are on and off the pedal continually, which over greases the tool.
    • When you are breaking thick concrete you may be on the pedal for a couple minutes at a time and then it under greases and the parts wear prematurely.

    I need some type of control system, at a reasonable price, that can accumulate the peddle time (closed circuit) and then send power to the greaser for a certain duration.

    Ex. Hammer hits for two minutes and then the greaser runs for five seconds. But the two minutes may not be continuous. 30 seconds at a time or what ever.

    All timer relays that I have seen reset when they loose their power (open circuit) and do not accumulate closed circuit time to accomplish this.

    I contacted an electronics store and they want to sell me PLCs for about 300.00 a piece and a one time 500.00 fee for the software to set them up.

    I am being told by a friend who plays with this type of stuff for fun that we could design and build a simple circuit board with a 555 timer, a decade counter, a relay and a few other diodes and resistors. I'm game but need help.

    The voltage from the pressure switch is 24VDC. I will need 24VDC 12amps output to run the pump.

    Can any body draw me a schematic to accomplish this?


  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Wat do you have for a hammer on control signal?