Electrical oddity

[kiwi belly tank]

Can somebody explain this!
I have two pinion direct drive over drive units (4WD) that are clutch packs applied by CO2 pressure through pressure drop switches to solenoids. I have a double redundant electrical system from the shifter & I installed some small LED lights to be able to quick check that both systems are working before a run. When I shift it, the LED's only flash one time when that circuit is powered up although the power is still on. If I disconnect then reconnect the light while the circuit is still powered up, the light will stay on.
The ground for these lights is through a ground switch so theoretically they would only come on by activating that switch to test but the lights actually have a less intense flash with no ground activated at all!
  Is it due to a voltage surge by the solenoid?
  Is there a way to fix this other than changing to incandescent lights?
   Sid.

[Stainless1]

Sid, can you sketch your circuit... as connected.... it might be easier to figure out.  Is you circuit grounding through the solenoid coil...

[Mike Brown]

Can somebody explain this!
I have two pinion direct drive over drive units (4WD) that are clutch packs applied by CO2 pressure through pressure drop switches to solenoids. I have a double redundant electrical system from the shifter & I installed some small LED lights to be able to quick check that both systems are working before a run. When I shift it, the LED's only flash one time when that circuit is powered up although the power is still on. If I disconnect then reconnect the light while the circuit is still powered up, the light will stay on.
The ground for these lights is through a ground switch so theoretically they would only come on by activating that switch to test but the lights actually have a less intense flash with no ground activated at all!
  Is it due to a voltage surge by the solenoid?
  Is there a way to fix this other than changing to incandescent lights?
   Sid.

Sid,

I suspect that you are having problems with back EMF.  Large solenoids generate large currents when activated and deactivated.  It is always preferrable to have a substantial diode connected reverse polarity across the solenoid as close to the solenoid as practical.  There could be a myriad of issues if you could supply a schematic of what you are doing it would help.   

[ronnieroadster]

Sid I added an LED indicator to the race car so I know when I'm finally in high gear.  I added a micro switch so that when the shift lever is in the engaged postion in high gear the small arm on the switch which is now being pushed will close the open contacts. One wire from this switch is connected to the transmission case so the LED gets its negative ground from this source and the other wire leaving the switch is feeding the LED indicator. The other side of the LED receives the positive battery side from the fuse block in the drivers compartment. There's few other current pulling devices in the area of all of this both at the transmission and the fuse block area but nothing effects the indication from working correctly.
 Ronnieroadster

[kiwi belly tank]

Can somebody explain this!
I have two pinion direct drive over drive units (4WD) that are clutch packs applied by CO2 pressure through pressure drop switches to solenoids. I have a double redundant electrical system from the shifter & I installed some small LED lights to be able to quick check that both systems are working before a run. When I shift it, the LED's only flash one time when that circuit is powered up although the power is still on. If I disconnect then reconnect the light while the circuit is still powered up, the light will stay on.
The ground for these lights is through a ground switch so theoretically they would only come on by activating that switch to test but the lights actually have a less intense flash with no ground activated at all!
  Is it due to a voltage surge by the solenoid?
  Is there a way to fix this other than changing to incandescent lights?
   Sid.

Sid,

I suspect that you are having problems with back EMF.  Large solenoids generate large currents when activated and deactivated.  It is always preferrable to have a substantial diode connected reverse polarity across the solenoid as close to the solenoid as practical.  There could be a myriad of issues if you could supply a schematic of what you are doing it would help.   

Mike, you have the answer to my question.
I was so disgusted with it last night I had to walk away to keep my composure.
What it's actually doing as I relook at it today, the lights don't do anything when the solenoid is activated, they flash when the solenoid is deactivated.
I'm just going to back to the 20th century where I belong & put some real lights on it.
  Sid.

[manta22]

Can somebody explain this!
I have two pinion direct drive over drive units (4WD) that are clutch packs applied by CO2 pressure through pressure drop switches to solenoids. I have a double redundant electrical system from the shifter & I installed some small LED lights to be able to quick check that both systems are working before a run. When I shift it, the LED's only flash one time when that circuit is powered up although the power is still on. If I disconnect then reconnect the light while the circuit is still powered up, the light will stay on.
The ground for these lights is through a ground switch so theoretically they would only come on by activating that switch to test but the lights actually have a less intense flash with no ground activated at all!
  Is it due to a voltage surge by the solenoid?
  Is there a way to fix this other than changing to incandescent lights?
   Sid.

Sid,

I suspect that you are having problems with back EMF.  Large solenoids generate large currents when activated and deactivated.  It is always preferrable to have a substantial diode connected reverse polarity across the solenoid as close to the solenoid as practical.  There could be a myriad of issues if you could supply a schematic of what you are doing it would help.   

Mike, you have the answer to my question.
I was so disgusted with it last night I had to walk away to keep my composure.
What it's actually doing as I relook at it today, the lights don't do anything when the solenoid is activated, they flash when the solenoid is deactivated.
I'm just going to back to the 20th century where I belong & put some real lights on it.
  Sid.

Mike is right. When the current in an inductor (solenoid coil) is turned off, the magnetic field collapses, generating a voltage in the opposite direction. That's why the LED doesn't emit any light when it is on but as soon as the current is turned off, it flashes.

[Peter Jack]

Sid, there are a lot of us fall in the same boat. The twenty first century arrived just a little too quickly!!!

Pete

[SPARKY]

we used an old style gm stop light switch  when  pressure is in the shift system the light comes on

[Jack Gifford]

... the lights don't do anything when the solenoid is activated, they flash when the solenoid is deactivated...

Sounds to me like the LED is connected backwards.
"LED" == Light Emitting Diode. Like any diode, it only conducts in one direction- anode positive/ cathode negative.
If you dislike polarity-sensitive indicator lamps, AC/DC LED indicators are available and cheap. They are sized about the same as others, except for being about 3/4" deeper (to house the miniature full-wave rectifier),

[kiwi belly tank]

I threw out the LED's but incandescent lights are about as rare as dial phones these days!

No, the LED lights were the right way.

The test lights are to be sure both redundant circuits are good before a run & this isn't for the main trans, these are the pinion drive clutch packs that operate on 400psi of CO2. There are a few ratio options with different combos depending on what works best in the real world so the pressure drop limiting switches will allow some adjustability for shift timing & quality & allow me to upshift or downshift them. One possible unusual upshift would be from 3rd direct to 2nd overdrive at about 380-ish but also from the start I wanted to be able to have engine braking all the way back to 1st gear for stopping. Along with all this there are 6 chute tubes & 4 wheel water cooled brakes.
  Sid.

[manta22]

Keep the LEDs. If they light up when the solenoid is ON, then they are wired correctly. As I explained, when the solenoid is turned off there is a brief surge in the opposite direction. In any case, any solenoid should have a diode connected across its coil. A diode such as a "1N4004" should do the job; connect the diode so the stripe on its body is facing the + terminal of the solenoid. The other diode lead should connect to the other terminal of the solenoid. This diode prevents arcing across switch contacts which leads to an early switch failure and also prevents voltage breakdown to drivers that may be used to control the solenoid.

A conventional coil ignition operates on the same principle of a collapsing magnetic field when the points open.

https://www.digikey.com/en/products/detail/nte-electronics-inc/1N4004/11645015