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diode failure

Started by kelLOGg, August 27, 2013, 05:01:41 AM

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kelLOGg

I put a PWM speed controller on my MP32 years ago and protected it against accidentally reversing the battery leads with a Radio Shack diode. I tested it for proper functioning before connecting to the PWM controller and it was working as intended. A few days ago I misconnected the leads and got big sparks! >:( >:(. I removed the diode and checked its resistance in both directions and got near 0 ohms. It had failed!!

Do you guys have any recommendations on how to make this failsafe feature actually failsafe?
Bob
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

dgdrls

sorry to hear  I'd offer these;
wire up one-way connectors/plugs
color code your connection points.

DGDrls



Magicman

Color coded tape, paint and/or zip ties.
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

pineywoods

There are these things called fuses  ;D Then use the biggest diode you can find.
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
100k bd ft club.Charter member of The Grumpy old Men

beenthere

Then it is like the toilet seat being up.... just takes once and the next time you remember.

So, you won't forget again...  ;D

But paint code or changing connectors if worried once isn't enough. ;)
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

TimRB

What are the current requirements and what diode did you select?

Tim

hackberry jake

The first truck I had had a "fusable link" I think thats what it was called. I hooked it up wrong once and the wire came apart at the link. From there on out it was just twisted and taped  ::)
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EZ Boardwalk Jr. With 20hp Honda, 25' of track, and homemade setworks. 32x18 sawshed. 24x40 insulated shop. 30hp kubota with fel. 1978 Massey ferguson 230.

kelLOGg

I am trying to get the human error out of the way. I have 2 deep cycle batteries wired in parallel for charging and series for operation so I am fairly regularly changing connections. (I also operate a loading/turning 12 VDC winch off one battery which has a high amp draw). Even though the wires and posts are color coded sometimes (once actually) I just screw up :-[. The blown diode was actually a diode bridge (all I could find locally) and I connected to two appropriate terminals to act as polarity protection leaving the other two as "spares" which I certainly won't use now. I don't recall the specs but it was in excess of what I needed. I have ordered a replacement (30 A and 1000 VDC reverse voltage).
http://www.mouser.com/ProductDetail/STMicroelectronics/STTH3010WY/?qs=FvSsTZlmX3CO0Sp1q2SUHA==
Before I install it, was that an OK choice? Thanks for the comments,
Bob
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

SPIKER

Keilog:

that is a Power Diode rated to handle up to 30 amps.   Not sure where you are intending to WIRE it though as you are a bit vague where you were intending to place it.   It would probably NOT work for any motors though due to inrush and start up loads on the motors.   It wont work for between the batteries unless you have a 10~or 20 amp 12VDC charger that you wanted to use a pair of diodes to separately charge the two batteries.   It will work for moderate loads too as a power thru )reverse voltage protection) for smaller loads or possibly the PWM modulators depending on the current requirements of the PWMs.

Mark
I'm looking for help all the shrinks have given up on me :o

kelLOGg

The diode will be placed between the + side of 24 VDC source and + input of the PWM. Sawing requires about 2 - 10A, returning the head ~10A and if the saw head hits an obstruction and stops its motion ~20A . The PWHM can deliver 25A. The motor never starts at full speed; I dial the speed up slowly - do you think the inrush current is >30A?
Bob
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

nk14zp

Put the diode across the positive  and neg then on the bat side put the fuse. PWM, diode ,fuse then bat.
Belsaw 36/18 duplex mill.
Belsaw 802 edger.
http://belsawsawmills.freeforums.org/

SPIKER

Quote from: nk14zp on August 28, 2013, 07:22:04 PM
Put the diode across the positive  and neg then on the bat side put the fuse. PWM, diode ,fuse then bat.

You can use the diode as a "spike suppressor" this way by having the + and - across the diode so power does not go thru the diode unless a relay on the PWM drops our or the motor the PWM is running is shut off quickly.   This can have a magnetic field collapse putting this high current surge into the - and back feeds other stuff causing issues in the electronics elsewhere.   With the blocking diode across + & - that surge goes back around and does not spike the - system.

If you PWM can draw 25 operating amps then that diode is undersized.   On electronic devices most times they are rated at a certain operating current based on % ON time.   So running 10 amps 50% of time is OK if the diode is rated above that load.   For most diode applications though you want to have one for THRU power applications you need to get one rated about 2X your full operating load and at least 1.5X the Max Load.

That would mean you want the diode to have at least a 35 or so amp peak for thru power applications for longevity.   There are versions that can be mounted on Heat Sinks too which helps them live much longer.

Mark
I'm looking for help all the shrinks have given up on me :o

kelLOGg

I avoided the diode alltogether and the frequent need to disconnect the PWM from the battery posts. I was overthinking the solution to this problem and finally came up with a simple one.  I achieve polarity protection by using an ordinary plug and receptacle where the receptacle is connected to the battery posts and only needs to be disconnected when the battery needs replacing. Then I simply plug in the motor controller; almost impossible to reverse the polarity. The pic shows wiring for 24VDC operation with the input to the PWM box unpluged. Thanks for the replies.
Bob


 
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

Kbeitz

This is what I use... I got them on everything...



 
Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

kelLOGg

Cool. I assume the leads cannot be interchanged.
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

Kbeitz

Only fit one way...
E-bay has them for sale...

Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

drobertson

Kbeitz nailed this one, I was thinking make one or the other with a screw on connector and leave the others like factory.  But the quick connect looks real handy, I forgot about those lil jewels,  seems like a no brainer,  good idea,
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

Kbeitz

I got them on all my trucks and tractors and anything else that takes 12 volts.
You can buy them by the lot on E-bay... it's cheaper when you buy about 10-20 at a time.



 
Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

charles mann

i know this is an OLD thread, but i found some info that will serve me use in the near future. 
similar to Kbeitz connectors. I have been using these connectors, which are a turn style, and charles mann proof as my used to tell me.
 
MILLER ELECTRIC Welding Insulated Twist Lock Connector - 49WM95|129526 - Grainger

the connectors can handle a LOT of amps, for extended periods of time. On my welder, i made it to where the "work" and ground" leads can NOT be connected wrong by accident, which if they were the same for both, a person could reverse the welding polarity without on accident. on my machine, it is made for + or - field polarity welding, so it wouldn't matter, but the majority of the time, since i only stick weld with it, i run it on+ polarity, as where i think like tig or mig, requires - polarity and hooking the leads up backwards could damage the unit. 

Iv also used these to connect winch leads with long runs to the tck/winch. would be good for helping to eliminate accidental reverse battery connection in the future
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

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