Electrical Circuit Help Needed

[gemini5362]

guys the relay thing is pretty obvious to anyone that has any kind of electrical knowledge. The problem is you have to find a place to mount the relays and if the tractor is where they can get wet you have to find waterproof relays or they might have a short life when the contacts corrode.

The diodes on the other hand are not really that hard to hook up. attach one diode to each switch terminal (not to the center one). Make sure they have the end with the band on it away from the switch terminal. Hook the green wire to each diode. (using a jumper wire between the diodes) Wrap the whole thing with electrical tape so that it cant short out and you are done. It will work perfectly and be the easiest installation you can do. My friend and I talked about this circuit while I was typing my first thread in this post. Between us we have over half a century of electronic experience. Get the relays if you want to but it will cost more money and be harder to hook up.

 

[Spudland_Dave]

guys the relay thing is pretty obvious to anyone that has any kind of electrical knowledge. The problem is you have to find a place to mount the relays and if the tractor is where they can get wet you have to find waterproof relays or they might have a short life when the contacts corrode.

The diodes on the other hand are not really that hard to hook up. attach one diode to each switch terminal (not to the center one). Make sure they have the end with the band on it away from the switch terminal. Hook the green wire to each diode. (using a jumper wire between the diodes) Wrap the whole thing with electrical tape so that it cant short out and you are done. It will work perfectly and be the easiest installation you can do. My friend and I talked about this circuit while I was typing my first thread in this post. Between us we have over half a century of electronic experience. Get the relays if you want to but it will cost more money and be harder to hook up.

As far as weather...I'm not overly concerned....they're going into a 3520 Cab machine and theres ample space under the console panel where the switch will go to put em. If it gets wet in there, I got bigger problems
Seems with this circuit everyone you talk to has an idea...guy here at work said to use the Diode thing. The way he explained it was a Diode is an "Electrical Check Valve" where current can only go one way...correct? But he went on to say I'd need to size em correct, etc... going with NO relays would be much easier like you say....what size Diode would I need.

I guess I dont care HOW it works, I just want it to work...

 

[gemini5362]

I am not sure how much current a solenoid pulls. I am sure that one of the hydraulic guys on here will probably be able to answer this a lot better than me. I am going to guess they probably will pull 1 or 2 amps. If so then just get a couple of diodes that will be good for 2 amps if they pull more then you just need to get a higher current capability. Radio Shack will have them as well as any electronic store. If you have a guy that rebuilds alternators near you go see them and see if they have any diodes that they can sell you. If you get one from alternator repair guys have them mark the cathode end for you. some of the press in diodes it is not marked as well. The cathode is the end with the band on it and should be the end that is not attached to the switch. You should not have to pay more than a couple of bucks for each diode. First and easiest stop might be radio shack.

 

[GreatWhitehunter]

I would go the relay route. Diodes are a good choice also but diodes can and do fail. I deal with this alot on the Gas Turbines at work. Diodes also don't hold up well with alot of vibration. While it's true relays also fail you won't be endangering the rest of the circuit and electronics. As for weather issues you could go with solid state relays. They'll hold up better for you.

Matt T.

 

[gemini5362]

I would go the relay route. Diodes are a good choice also but diodes can and do fail. I deal with this alot on the Gas Turbines at work. Diodes also don't hold up well with alot of vibration. While it's true relays also fail you won't be endangering the rest of the circuit and electronics. As for weather issues you could go with solid state relays. They'll hold up better for you.

Matt T.

That is amazing I have been dealing with diodes for over 40 years. A lot of that time was on board naval vessels. The first 4 years of which we had a bent prop that caused the ship to shake a lot. I have replaced thousands of relays. Other than a short or something electrical happening I have never seen a diode go bad from vibration. Everyone is entitled to their opinion but in his application diodes would be a nice easy way to go. Oh and by the way a lot of relay circuits have diodes installed accross the coil to cure issues from induced voltages when the fields collapse in the coil as the relay is turned off and on.

 

[ampsucker]

i really think some might be over thinking this a bit.

my understanding is diodes are used with solenoids and other inductive loads to protect "micro" switches. this guy has a switch rated for 20 amps and is switching 2 amp loads. the solenoids will wear out before the switch does from arcing.

as far as relays go, same deal. i don't see the need for a diode or a relay after the switch. the loads do not justify it. a useful place for the relay might be in front of the switch triggered by a hot wire when the key is on just to shut everything down when the key is off.

otherwise, i would wire it as in larry's diagram (without the diodes) and go. just size conductors for the load, and fuse for the conductors. if you don't like the performance, you can update the circuit later on to do fancier stuff, but i think this should get you going.

anyone care to educate me on why this needs to be more complicated?

amp

 

[John47]

Diodes are not subject to damage or failure through vibration, higher voltage or more current than they can handle yes, high temperature yes.
I've worked with diodes for well over 45 years and the only problems I had was transients, spikes or whatever you want to call them. We used them in mining machines in the pilot circuits and later in all forms, power, LED's etc in modern power loading machines where vibration is at it's highest.
There are several in continuous miners, and they stand up exceptionally well to vibrations.
Try the ones mounted in the terminal chambers of armoured face conveyor motors, loads of vibration, yet again failure rate, very low and fail to open circuit, transients once more. "high voltage" induced by the opening and closing of the power circuit.
Diodes are exceptionally reliable in use.
(Maintenance electrician for 45 years)

 

[yankeerider]

...What I'm trying to do is to wire up the 3 bank Hydraulic Diverter from Surplus Center.....Correct

The description of that valve says there's a check valve in the "A" port of the 3rd bank. Is that check valve readily removed?

 

[Wayne County Hose]

As stated, diodes are exceptionally reliable. I have changed way more relays than diodes. The only reason I recommend relays over diodes here is that a relay is LESS complicated for this installation, more reliable, and easier to troubleshoot/install for the man doing the job. Will someone tell him exactly what size diode he needs, part # and where to get it? You can go to an auto store and ask for a fog light relay and you're done. Yes, a factory would install diodes and be done with it. They have engineers to choose the correct parts that will all electrically match-up. This gentleman does not have that capability. If anyone here does, please provide part # and vendor so that he can order.

 

[gemini5362]

i really think some might be over thinking this a bit.

my understanding is diodes are used with solenoids and other inductive loads to protect "micro" switches. this guy has a switch rated for 20 amps and is switching 2 amp loads. the solenoids will wear out before the switch does from arcing.

as far as relays go, same deal. i don't see the need for a diode or a relay after the switch. the loads do not justify it. a useful place for the relay might be in front of the switch triggered by a hot wire when the key is on just to shut everything down when the key is off.

otherwise, i would wire it as in larry's diagram (without the diodes) and go. just size conductors for the load, and fuse for the conductors. if you don't like the performance, you can update the circuit later on to do fancier stuff, but i think this should get you going.

anyone care to educate me on why this needs to be more complicated?

amp

If I am understanding what he wants to do the problem is energizing the green coil when either of the other two coils are energized. If he just attached the positive wire from the green coil to both sides of the switch then he positive side of the other two coils one to each side of the switch. When he puts the switch in either position the wires to the green coil will act like a jumper accross the switch and energize both of the other two coils also. As someone mentioned in one of the other posts the diode will act like an electric check valve allowing current to flow in one direction only and will block current from energizing the other side of the switch at the same time. The issue that is being discussed is not whether he needs a diode or a relay but which would be better for him to use.

 

[Spudland_Dave]

If I am understanding what he wants to do the problem is energizing the green coil when either of the other two coils are energized. If he just attached the positive wire from the green coil to both sides of the switch then he positive side of the other two coils one to each side of the switch. When he puts the switch in either position the wires to the green coil will act like a jumper accross the switch and energize both of the other two coils also.

Seriously, I think thats the best explaination posted yet...

That being said....My search for an OEM DPDT switch is getting closer...I'm now trying to deal with a vendor who carries some switches which might work...

 

[gemini5362]

As stated, diodes are exceptionally reliable. I have changed way more relays than diodes. The only reason I recommend relays over diodes here is that a relay is LESS complicated for this installation, more reliable, and easier to troubleshoot/install for the man doing the job. Will someone tell him exactly what size diode he needs, part # and where to get it? You can go to an auto store and ask for a fog light relay and you're done. Yes, a factory would install diodes and be done with it. They have engineers to choose the correct parts that will all electrically match-up. This gentleman does not have that capability. If anyone here does, please provide part # and vendor so that he can order.

Do you know what typical amperage draw for solenoids he is talking about. I did look at radio shack and they have these:

6A, 50V Rectifier Diodes (4-Pack)
Model: 276-1661 | Catalog #: 276-1661

RadioShack.com

That is a 4 pack for $2.49 I cannot imagine that they would not do the job. The url is for ordering them online but a local radio shack store might have them.


The only problem with hooking up a realy is knowing how to hook it up some times. If you dont have experience sometimes you can get the wrong wire on the wrong terminal. and he would need a double pole relay. and then he would have to have the green wire on a normally closed pole for one switch and a normally open pole for the other switch and hook the relay up so that it energized when he threw the switch in one direction only. childs play for someone with electrical or electronic experience but not easy if you have not played with that kind of thing. The diode I can tell him to hook it up so the band end is not attached to the switch and those are pretty easy directions to follow for someone with out experiences in those matters. I dont have to know what pins to hook to like I would if I told him to hook up a relay

 

[John47]

Some companies that deal on line with electrical and electronic parts are ..
Jameco.
MCM Electronics.
Allied Electronics.
Newark dot com.
All good reliable and cheap, and highly recommended.
ONLY deal with Ratshack if your desperate and can't get them elsewhere, they are expensive and their parts are of questionable quality.

One last point, if you use diodes, make sure you place a shunt diode across the valve coil, or the main diodes won't last very long, the back emf generated when you switch off will be high enough to destroy the diodes.

 

[Wayne County Hose]

One last point, if you use diodes, make sure you place a shunt diode across the valve coil, or the main diodes won't last very long, the back emf generated when you switch off will be high enough to destroy the diodes.

So there is another issue if diodes are used? I can remember repairing the computerized forklifts, some rookies used to remove the suppressor blocks from across the switches and coils. "You don't need those things, they don't do anything anyway." Yep, never changed so many switches after that.

 

[John47]

So there is another issue if diodes are used? I can remember repairing the computerized forklifts, some rookies used to remove the suppressor blocks from across the switches and coils. "You don't need those things, they don't do anything anyway." Yep, never changed so many switches after that.

Sure is a reason, in transmitters we always have a shunt diode across the coils of relays, or the very delicate CMOS chips would get fried.
Relays are inherently dangerous in explosive atmospheres, to provide protection a shunt diode is placed across the relays coil in reverse to short the back emf out when the relay open de energises. Usually the diode is rated about 1000PIV.
Thats Peak Inverse Voltage.

 

[madslick]

Sure is a reason, in transmitters we always have a shunt diode across the coils of relays, or the very delicate CMOS chips would get fried.
Relays are inherently dangerous in explosive atmospheres, to provide protection a shunt diode is placed across the relays coil in reverse to short the back emf out when the relay open de energises. Usually the diode is rated about 1000PIV.
Thats Peak Inverse Voltage.

Yeppers,
The backwards diode will provide a place for the current to go when you shut off the juice to the Relay coil.
Remember ELI the ICE Man?
ELI >> V = L dI /dt >>> so you get a huge voltage spike (arc) if you shut off the current and you don't have a place to dump the current.

check to make sure that the relays aren't allready protected with a built in diode.
If not, then instal one backwards directly across the coil terminal as John47 recomended.

Later,
Rick

 

[gemini5362]

actually the only thing you have to worry about hurting is the diodes that he uses with the switch. With a big enough voltage rating that wont hurt them either. If he spends less than ten bucks on diodes and hooks them up Like I suggested he will probably find the circuit works very well and will last for a long time. We are trying to over engineer this whole problem for him. The best engineer I ever knew was one of my college professors. I was a lab assistant working with him one time and I watched him design a small circuit. He basically said what have we got to work with and then just picked something close. Yes there is a possibility of a large voltage spike from the coil on the solenoids. but that is not a given that it will hurt anything.

 

[Spudland_Dave]

Thanks for all the help guys...BUT...I was able to track down the OEM Supplier to Deere for the 3x20 and 4x20 series switches and was able to order a DPDT Factory OEM Switch...SO...if anyone is interested in any, shoot me a PM as I had to order a bunch of em (Minimum order amount )
That also means, No "Fancy" Wiring is needed....