Hello,

I'm only a bit electrically inclined so please forgive my lack of knowledge in these matters.

There's a machine here which requires air blow-off inside it.
Previously controlled manually, I am automating this air-blow off so that it turns on automatically.

I have a 24v DC pneumatic solenoid, and when 2 condition are met, "door closed" and "laser ready", I want the solenoid to activate and pass the air.

I've identified the contacts that go from 0v to 24v for each of these conditions, and can wire either to the solenoid and it works for one condition. But how would I go about having a single solenoid activate under the condition that BOTH the door is closed and the laser is ready?

I need to make sure I keep the inputs separate so one doesn't feed 24v into the other and cause machine errors.

I can solve this by just using 2 separate solenoids on the air line, one for each condition, but we want to use just one solenoid for less potential failure.

Thanks for any guidance.

 

Two relays picked up by each condition and a contact on each AND'ed or in series with the solenoid.
Max.

 

I sketched up a solution and ordered the relays.

Thanks for the reply.

 

Two relays picked up by each condition and a contact on each AND'ed or in series with the solenoid.
Max.

"The secret of good communication is: brevity" ...

 

Two relays picked up by each condition and a contact on each AND'ed or in series with the solenoid.
Max.

You can do it with only one relay. Activate it's coil with the 24 V from the "laser ready" and activate the solenoid with the 24 V from the "door closed", fed through the normally open contacts of the relay.

 

WOW thanks so much guys. I almost feel embarrassed I didn't think of these solutions.

Best Regards

 

WOW thanks so much guys. I almost feel embarrassed I didn't think of these solutions.

Best Regards

With this forum you are gaining access to MANY years of experience across a wide variety of fields. So don't be too embarrassed.
I was going to suggest putting the switches in series, before realizing that they were already connected to other parts of the system. But since you are connecting an inductive solenoid, you do need to put a snubber across the coil to protect the other parts of the system. AND you need to be sure that there is enough current capability to power that solenoid valve. You may have come across two low-powered circuits not able to power the added load of the solenoid coil.

 

You may have come across two low-powered circuits not able to power the added load of the solenoid coil.

In which case you may have to use Max's two relay solution.

 

Thanks so much MisterBill2. Here's a quick sketch.

There is enought current I tested each on the solenoid. I'll have to see what the relay draws, though. I bought a couple bosch style 24v dc relays with harnesses.

Could you tell me more about this snubber, and how I incorporate it into the wiring?

 

Thanks so much MisterBill2. Here's a quick sketch.

There is enought current I tested each on the solenoid. I'll have to see what the relay draws, though. I bought a couple bosch style 24v dc relays with harnesses.

Could you tell me more about this snubber, and how I incorporate it into the wiring?

In this case the snubber would be connected in parallel with the solenoid coil so that it would absorb the inductive voltage spike when the solenoid was de-energized. A snubber consists of capacitor and resistor in series, the values depend on the current and voltage in the circuit. AND while the relay is shown in the right location, to be useful the drawing needs to indicate which connections are the relay contacts and which are the coil that operates the relay.

 

In this case the snubber would be connected in parallel with the solenoid coil so that it would absorb the inductive voltage spike when the solenoid was de-energized. A snubber consists of capacitor and resistor in series, the values depend on the current and voltage in the circuit. AND while the relay is shown in the right location, to be useful the drawing needs to indicate which connections are the relay contacts and which are the coil that operates the relay.

Thanks again, I understand. To save from ordering extra parts I will probably use the 2 relay configuration and bring 24v dc power directly from the machine's power supply to keep everything isolated.

 

Could you tell me more about this snubber, and how I incorporate it into the wiring?

I would use a simple diode, reverse biased across the coils, the cathode (stripe) goes to the positive supply end.
You may want to place one across both relay coils also, as well as the solenoid.
Any of the 1n4xxx range would work for the relays, and should also be OK for the solenoid.
1n4005-7 etc.
R/C snubbers are most often used on AC circuits, for DC you can use the customary rectifier.
Max.

 

I would use a simple diode, reverse biased across the coils, the cathode (stripe) goes to the positive supply end.
Yoy may want to place one across both relay coils also, as well as the solenoid.
Any of the 1n4xxx range would work for the relays, and should also be OK for the solenoid.
1n4005-7 etc.
R/C snubbers are most often used on AC circuits, for DC you can use the customary rectifier.
Max.

While diode protection is a very good approach, it is vital to observe the diode polarity in every connection. I recall a production machine being out of service for several days because of reversed connections to a relay that had an internal diode that had not been noticed, and so had been connected backward. All spike prevention diodes should be installed so that they are visible and their polarity is obvious.

 

I recall a production machine being out of service for several days because of reversed connections to a relay that had an internal diode that had not been noticed, and so had been connected backward.

This is why it is imperative to have the data sheet on the relay when installing, these are usually marked, at least the type that I use.
Looks like oversight by the enclosure wirer.
Max.