kennyd
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Remote valve is OC. The 3PH valve is usually the last valve in the circuit by default.
Do I need a relay for grappel?
- Thread starter Dale1995
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Remote valve is OC. The 3PH valve is usually the last valve in the circuit by default.
eepete
Platinum Member
AKKAMAAN: the Radio Shack page doesn't say what kind of diode that is. The diode needs to be a high speed one, not one for line AC rectification. The difference is the response time. The 50 volts PIV makes me think it might be fast enough. All that said, if it's worked for you for a long period of time then it must be OK for both clamping speed and spikes that exceed the PIV from other coils in the system. Anyway, do you have a real JEDAC number for the part?
2nd thought: May not be a big deal here, but, the diode across the coil like that tends to slow down the release time of the relay. Using either an MOV (like a 18 to 24V MOV) or a small resistor in series with the diode allows the stored energy in the coil to be dissipated outside of the coil (in the MOV or resistor) which speeds up the release time and speed. Again, it may be in this application it doesn't matter. And if you oversize the relay the contact life will be OK even with a slower release. But if you've had problems with the relay contacts or the diode popping, then this could be looked into more.
3rd thought: My preferred part for this sort of thing is a power transient zener diode. It can be used for relay clamping, and can take the spikes you see from things like starter motors without have the problem you get when the spikes exceed the PIV rating. It will also do a better job when something puts ringing voltage on a line. Drawback is probably that it's not a Radio Shack part, so have to order it for real. I've used back to back TVS diodes for relay clamping to get the best of all worlds. Energy dissipated in the diode, no PIV problems, and spikes get clamped.
I've just seen too many people pop a rectification diode like a 1N4004 across a relay coil, and it's just too slow to help much.
Pete
2nd thought: May not be a big deal here, but, the diode across the coil like that tends to slow down the release time of the relay. Using either an MOV (like a 18 to 24V MOV) or a small resistor in series with the diode allows the stored energy in the coil to be dissipated outside of the coil (in the MOV or resistor) which speeds up the release time and speed. Again, it may be in this application it doesn't matter. And if you oversize the relay the contact life will be OK even with a slower release. But if you've had problems with the relay contacts or the diode popping, then this could be looked into more.
3rd thought: My preferred part for this sort of thing is a power transient zener diode. It can be used for relay clamping, and can take the spikes you see from things like starter motors without have the problem you get when the spikes exceed the PIV rating. It will also do a better job when something puts ringing voltage on a line. Drawback is probably that it's not a Radio Shack part, so have to order it for real. I've used back to back TVS diodes for relay clamping to get the best of all worlds. Energy dissipated in the diode, no PIV problems, and spikes get clamped.
I've just seen too many people pop a rectification diode like a 1N4004 across a relay coil, and it's just too slow to help much.
Pete
AKKAMAAN
Veteran Member
I can hear/read that you have way more all round experience about semi conductors than I have....but I have dealt with this, thru my 25 year hydraulic experience, and I have only used regular generic diodes, rectifier or other appropriate ones...the faster they let the energy from the spike release thru the diode the better...
I would not choose a Zener diode....that would delay the release of the spike energy....I would choose a diode with a low forward voltage drop....
For this prpose it is not a real big deal...for the valve coil you can use this one...
No, that's not going to happen...
No it does not matter
This vhigh voltage spike has nothing to do with contact release time....
This diode eliminate 99% of the wear on the relay or switch contacts..
I would not choose a Zener diode....that would delay the release of the spike energy....I would choose a diode with a low forward voltage drop....
eepete
Platinum Member
AKKAMAAN: OK on all that. Sounds like all the 2nd and 3rd order details just don't matter here. Gotta love something that works 
In the "knowledge just for fun" department, the simple diode means that the energy stored in coil has to be dissipated in the coil. So the release time does get longer, and the contacts release with less of a "snap". Again, here it doesn't seem to matter. This is also why the MOV or back to back zener results in faster release. More energy is dissipated in devices instead of the coil.
The zener doesn't delay the release of the energy. In fact, it looks just like the plain old diode (but a high speed one) because you use it in a forward biased mode, not in the zener mode. The zener part of the diode just means you have less worry about exceeding the PIV rating with spikes on the power line since the part is designed to "get kicked" by them.
At any rate, you've got a tested solution with readily available parts. I suspect it also doesn't hurt that the number of cycles the relay gets per year is probably low (<2500 or so?).
Pete
In the "knowledge just for fun" department, the simple diode means that the energy stored in coil has to be dissipated in the coil. So the release time does get longer, and the contacts release with less of a "snap". Again, here it doesn't seem to matter. This is also why the MOV or back to back zener results in faster release. More energy is dissipated in devices instead of the coil.
The zener doesn't delay the release of the energy. In fact, it looks just like the plain old diode (but a high speed one) because you use it in a forward biased mode, not in the zener mode. The zener part of the diode just means you have less worry about exceeding the PIV rating with spikes on the power line since the part is designed to "get kicked" by them.
At any rate, you've got a tested solution with readily available parts. I suspect it also doesn't hurt that the number of cycles the relay gets per year is probably low (<2500 or so?).
Pete
wildwillie
Silver Member
I picked up a switch at my local Honda ATV dealer for $20.00 Two position momentary and water resistant. it is for a wench.
AKKAMAAN
Veteran Member
pricy!!...Was that a high Amp switch then??
I think I would have tried another source...(online)......LOL...unless I was stranded...
Brad_Blazer
Veteran Member
If you use a solenoid valve like the ones linked they are plumbed like control valves and you want the "in" and "out" ports of each valve set in series on the circulating "power beyond" loop. All of the work ports should be independant. The solenoid valve should come last since most do not have a low pressure return line separate from the outlet port (aka "power beyond").
DiskDoctr
Platinum Member
Thanks, Brad, for your reply. I've started a new thread here:
Hydraulic system diagram with factory remote and DA Questions - TractorByNet.com
I think it shows what you mention. Any tips on that thread is most appreciated, too.
- JC