Question Regarding Electro-Mechanical Relay

[Edwards749]

Currently we have experienced a slower than optimal reject rate on one of our machines. The reject station is operating an air solenoid and was controlled by an output module. As an experiment the module now controls a mechanical "dry contact" relay which then activates that solenoid. Both configurations where watched using a scope meter and found that the relayed configuration was operating earlier and for a longer period of time than running straight from the module. This cause the reject rate to operate at a much better pace. Does any one have an explanation as to why this maybe be?

 

[Skogsgurra]

Depends on a lot of things. Solenoid DC or AC, Realey DC or AC, operating near rated voltage or above/below, snubbers, free-wheeling diodes. Things like that.

BTW, is it a sheet cutter? Jagenberg, perhaps?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

It may be interesting to put your scope on the output of the module when operating the solenoid directly and with the relay in the circuit. The waveforms may go a long way to suggesting an answer.

Bill
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"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Most PLC I/O incorporates a diode on their solid-state I/O, which would give a longer drop-out time than a mechanical relay without a diode.


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If we learn from our mistakes I'm getting a great education!

 

[OperaHouse]

That diode off delay problem in the I/O can be solved by placing a diode in series with the relay. Any 1A diode of several hundred volts should be sufficient. I assume the faster turn on is not a problem or can easily be solved with either a mechanical or software solution.