Diverter on JD H260 - switch problems

[Industrial Toys]

I just showed a friend how to wire a four channel radio remote control to a hydraulic power pack. The relays claim 20 amps and it works for now, but I am skeptical. That is what the hydraulic shop offered him. I did add 1N4001 diodes to all coils. That is only around 100 PRV if I am correct, but I have never seen commercially designed stuff go nuts on the ratings for such protection diodes.

In general, most switch and relay contacts have the highest ratings for AC current. DC is MUCH harder on a contact.

I ALWAYS use an intermediate relay when designing such stuff and never put more then this low coil current through my control circuits. It adds complexity and cost but has served me well.

 

[KY Gun Geek]

Got my hands on another switch and some diodes today. Switch is same as above. Diode is 50v, 6A. The 50v is a little light, but I figured I would give it a try. I have some 1000v 10A coming.

Before I get to the install I did a little science experiment. I touched wires together (to simulate switch contacts) and videoed the arc. I then wired in the diode, and did the same thing. There is a noticeable difference in the sound, size, and intensity of the arc. Below should be some stills clipped from the vid.

However, again, the switch lasted about 30 to 45 minutes of me picking up brush (the job that is not getting done cuz I am fool'n around with the tractor). More details, and my next step in the next post...

 

[KY Gun Geek]

As stated above, wired in a diode and a new switch. Switch failed again in about 30 to 45 minutes of operation, maybe 25 or 30 cycles.

When I got the switch, I got an extra switch, and per the discussion above, I got a relay. My source for the diode is Radio Shack, and the switch and relay is Autozone. Diode is 50v at 6A, switch 8A. The diode is a little light for this duty. I have some 1000v/10A diodes, and a 5A switch coming from Amazon.

Some pics below of the diode install. Had to get after the connector with the dremmel - the diode is pretty big. The diode is installed so that it is reverse biased when battery voltage is applied to the side with the band (red wire is +12v when switch is pressed, black wire is grounded)

Given the difference seen in the arc, was really surprised when the switch failed again. I thought the diode had failed open (it is not up to the spec discussed above), and that caused the switch to fail. I tested the diode with my DMM (it has a diode test setting). Diode tested as open when reverse biased, and shows 5287 when forward biased. I'm not sure what this number actually means (diodes have a voltage drop and small forward resistance, so I'm assuming this is just how the meter reads that). Anyway, the key was that the diode I had installed and all the other diodes in the package (there were 5 total) read almost exactly the same. So they were all good (or bad) but the installed one tested the same as the unused ones. I must say I rigged up a little circuit to test the diode (diode and a resistor) and it worked as I would have expected - current flowed in forward bias, did not flow in reverse bias. I don't trust gravity right now either.


I did a test rig of the relay and it worked fine. The switch current will be 0.14A according to my meter, so let's hope it can handle it. I will leave the diode in the diverter solenoid to give the relay contacts as much help as possible. So tomorrow I'll install the relay and try to move some slash!

Will probably switch to the higher rated diodes when the arrive next week.

Any other ideas are welcome at this point. If the relay fails, I'm stumped. I have been searching this and a couple of other boards, and while I see people discussing using a diode, and a few saying they did it, I don't see anybody with this level of problem killing switches...

 

[KY Gun Geek]

Think about how long a set of points would last on a gas engine. Points opened and closed 100's of times a minute and would still last 5-10 years under normal use.

There's more going on there.

Points also need a condenser (capacitor) or they burn in a hurry.

 

[BukitCase]

"Points also need a condenser (capacitor) or they burn in a hurry."

Exactly - been a long time, but I used to remember which way it went; if you got the wrong capacitance (either from some parts guy picking up the wrong box, cap failure, etc) too MUCH capacitance would pit the points in ONE direction, too LITTLE would pit them the OTHER way. The RIGHT amount for the particular coil, and the "tank circuit" is BALANCED (minimum current OUTSIDE of the "tank circuit") and the points last a LONG time.

Same effect (and for the same reasons) as welding - material deposition follows electron flow. DCEN (STRAIGHT polarity) gives more deposition but less penetration because the negative side is ALSO heating up more, although that's MOSTLY because the MUCH smaller cross-section ELECTRODE is providing all that current while the WORK can (usually) spread the flow out over a much larger area.

Not sure if these would be available LOCALLY, but we used to use "snubbers" in a lot of places - looks like a capacitor of sorts, but contains a cap AND a resistor in SERIES - placed across an inductive load along with the (paralleled) diode, they can reduce the inductive effect so the diode doesn't have to do it all.

BTW, it's possible that the reason your diode tests OK but didn't SOLVE the problem - MIGHT be because your diode is rated for enough CURRENT that it doesn't fail PERMANENTLY when the counter emf spike hits it - under some conditions, semiconductors can "break down" and allow reverse current but then "heal" themselves if it's short term enough and doesn't generate enough heat -

If you have access to a scope you might be able to do a more quantitative experiment (actually put NUMBERS to each scenario), that'd make it faster to "dial in" a fix for your specific situation - my own projects involving solenoid diverters are too far down the (Looooong) project list to be of much help to you now, but I'm pretty sure that when they reach the top of that list there WILL be more info forthcoming (assuming my Tektronix scope still works, it's been decades)

Hope SOME of the above helps, good luck on your "quest for (NO) fire" :thumbsup: ...Steve

 

[KY Gun Geek]

Relay wired in - set up worked longer than the previous 45 minutes. Will give it a bit of a work-out tomorrow (2 or 3 hours).

 

[tre873]

Relay wired in - set up worked longer than the previous 45 minutes. Will give it a bit of a work-out tomorrow (2 or 3 hours).

Glad you got it working.

 

[KY Gun Geek]

About 10 hours of run time and the relay seems to have solved the problem!

As many folks are talking about diverter valves, I hope this thread helps!