Electrical Circuit Help Needed

[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....