HELP NEEDED: Solenoids not firing

[gpetilli]

Originally Posted by Mark McLeod

I've had solenoids that were directional.
The LED generally turns on, but the coil does not trip when wired backwards.

If they are pulsing too quickly, then that will show up on the PCM indicator per solenoid.
For a double solenoid, if the PCM light is on then the solenoid will be driven to the corresponding position. If the light is off, then the position is indeterminate. If both sides of the solenoid are tripped at the same time then it's also not going to move.

For a single solenoid, the PCM light has to be on for the solenoid to move away from the home position. When the PCM light is off a single solenoid will return to the home position.

Good point - if double solenoid and pulse both nothing happens!!! If they are double solenoids, unplug one side and try it then repeat for other side.

[larak]

Originally Posted by Mark McLeod

I've had solenoids that were directional.
The LED generally turns on, but the coil does not trip when wired backwards.

If they are pulsing too quickly, then that will show up on the PCM indicator per solenoid.
For a double solenoid, if the PCM light is on then the solenoid will be driven to the corresponding position. If the light is off, then the position is indeterminate. If both sides of the solenoid are tripped at the same time then it's also not going to move.

For a single solenoid, the PCM light has to be on for the solenoid to move away from the home position. When the PCM light is off a single solenoid will return to the home position.

We have single solenoids. This kind in particular: http://www.automationdirect.com/stat...lenoidavs3.pdf

We will try to increase the pulse time once we unbag our robot.

Thanks for the responses!

[gpetilli]

Problem solved.

From the data sheet:
• 2-position, single solenoid normally closed spring return;

Since it is normally closed, when the solenoid is not powered, the spring returns it to the closed position. These solenoids need you to hold the the 24V on the coil, not pulse it.

To be clear, you have the ones with only one black wart with wires, correct?

[larak]

Originally Posted by gpetilli

Problem solved.

From the data sheet:
• 2-position, single solenoid normally closed spring return;

Since it is normally closed, when the solenoid is not powered, the spring returns it to the closed position. These solenoids need you to hold the the 24V on the coil, not pulse it.

To be clear, you have the ones with only one black wart with wires, correct?

If by wart you mean thing that the wires come out of, then yes.

[larak]

Update:

We tried working backwards on our other identical robot. We tested the voltage going to the solenoids forwards and reverse and it actuated with 24v. With only 12v the solenoids light up, but don't actuate. The pulse in code is 0.25 seconds and works perfectly fine on this robot (the code is identical for both).

On our competition bot (the one that doesn't work) we are going to oscope and multimeter the signal from the PCM to solenoid and if it is correct (24v and 0.25sec pulse) we will swap out the solenoid and if it is not correct we will swap out the PCM.

[gpetilli]

Originally Posted by larak

If by wart you mean thing that the wires come out of, then yes.

Yes. That means it only has one active coil and the other direction is activated by a spring. On a dual coil solenoid you pulse A or B to set the position and an air "pilot" holds it in the last commanded position.

On the single coil solenoid that you have, the spring holds the position to normally closed (lets call it A) and to switch to open (B) you energize the coil. You need to hold the coil energized for the entire time you want the solenoid open, because the spring returns it to normally closed whenever the coil is not energized. If you don't pulse it, but hold the value you should be fine. The manual button activivation works because the data sheet specifically says it latches.

Good luck at your competitions.

[gpetilli]

Originally Posted by larak

Update:

We tried working backwards on our other identical robot. We tested the voltage going to the solenoids forwards and reverse and it actuated with 24v. With only 12v the solenoids light up, but don't actuate. The pulse in code is 0.25 seconds and works perfectly fine on this robot (the code is identical for both).

On our competition bot (the one that doesn't work) we are going to oscope and multimeter the signal from the PCM to solenoid and if it is correct (24v and 0.25sec pulse) we will swap out the solenoid and if it is not correct we will swap out the PCM.

Yes, a 24V coil needs 24V to work reliably. The diode lighting at 12V happens on some 24V solenoids, but even then unreliably. The coil on the solenoid should be marked with the voltage and you need to use the correct voltage. ALL solenoids on one robot need to use the same 12V or 24V voltage coils and the PCM must be have its jumper set for that voltage.

If you have single coil solenoids, you should not pulse the coil - it returns to the normally close position when the coil is not energized.

[larak]

Thanks for all the suggestions everyone! We fixed the problem by replacing the pcm.