Add a diode to my solenoid valve?

[IceStationZebra]

You don't absolutely need a diode if the switching mechanism can handle the voltage spike, but they don't hurt to have in the circuit either. Often times the diode is built into the coils themselves. You can tell if one wire is specified as the positive lead or sometimes they will have a diode symbol.

Coils may also be supplied with a diode bridge, especially common in coils design for AC or DC operation, in which case polarity is not important because the clamping action will work either way.

I'm not sure there is an easy way to measure the coil with a meter to determine if a diode is present. I'm thinking no because the internal battery in a DMM would have to have sufficient voltage to bias the diode open, and they are usually <9vdc. If you have a part number it should tell you one way or the other.

ISZ

 

[Bigshooter81]

So looking at my solenoid valve, soldered between the negative and positive terminals is an LED.... will this act as a suppression diode as well?

 

[Soundguy]

You commonly see diodes on relay circuits. In vehicle fuse boxes they are often listed as relay protection.

Anode to negative, cathode to positive.

Many diodes just have a stripe on cathode side.

Dont get a zenir diode, and make sure it is something like 50PIV.

 

[buickanddeere]

Prevents a damaging high voltage spike in the opposite direction of normal current flow.

 

[RNeumann]

I'm assuming this is 12v tractor stuff. What are you switching? Type of load, amps etc. Adding a diode is not a common practice for typical automotive/tractor applications......so I'm curious!

I should have worded this better. What brand and model valve? Most valves have the diode or some other design feature to prevent the voltage spikes. This is more than likely much ado about very little.

 

[Bigshooter81]

Chief directional solenoid valve..... and as noted above, there is an led that is wired parallel to the coil right at the terminal..... Is this sufficient to protect the switches?

 

[RNeumann]

I can't find much about the Chief brand of valves so I have no idea how the valve electronics are designed. If you are worried that your switch life will be shortened to the point adding a diode or other over voltage protection will help I'd throw it in.

 

[dfkrug]

You don't absolutely need a diode if the switching mechanism can handle the voltage spike, but they don't hurt to have in the circuit either. Often times the diode is built into the coils themselves. You can tell if one wire is specified as the positive lead or sometimes they will have a diode symbol.

Coils may also be supplied with a diode bridge, especially common in coils design for AC or DC operation, in which case polarity is not important because the clamping action will work either way.

I'm not sure there is an easy way to measure the coil with a meter to determine if a diode is present. I'm thinking no because the internal battery in a DMM would have to have sufficient voltage to bias the diode open, and they are usually <9vdc. If you have a part number it should tell you one way or the other.

You beat me to it.

My last few HydraForce solenoid valves would operate properly regardless of how I connected up
my 12VDC polarity. That means it had a rectifier in there. I don't know if most brands do it that way
these days.

Either way, I try my solenoids with a 12VDC battery and wire to see what kind of spark I get.
If significant, I want to protect my switch from inductance with a diode. I just scavange the
diode off an old circuit board.

Forward turn-on voltage (phi) for diodes is commonly about 0.6-0.8V.

 

[bigdeano]

My last few HydraForce solenoid valves would operate properly regardless of how I connected up
my 12VDC polarity. That means it had a rectifier in there.

A solenoid will ordinarily operate the same with either polarity even if there's no diodes in it. It just tries to center the iron plunger in the magnetic field. The polarity doesn't matter unless the plunger is a permanent magnet, which isn't common.

 

[Texasmark]

The diode in electronic circuits is always installed in parallel with the coil. Anode (arrow) is connected to the low/ground side of the coil of the relay/solenoid.

Lets see if this makes sense: when the solenoid is energized, it creates a magnetic field to pull/hold the armature/contacts. When the solenoid is de-energized, that existing magnetic field collapses, which induces a reverse polarity voltage, which tries to keep the current flowing in the coil. This reverse voltage is snubbed out by the diode, and therefore no other sensitive circuits are disturbed.

Yes sir you are correct.

Only place I have seen an "inverse clamping diode" was in electronic circuits where the transient voltage, or the " electrical noise" generated by it couldn't be tolerated. For wiring such as tractor wiring harnesses, the battery itself is a good snubber and no diode is required.

In today's new tractors with ever increasing electronics, it may be wise to incorporate one. However, a responsible electronics designer would incorporate his own safeguards in the design of the equipment. If he/she doesn't have reign over the design of the end item then the safeguard needs to be incorporated in the circuit assembly.....no biggie, just put an inverse diode on the power source to the circuit....cost? Pennies.