Author Topic: Hall Sensors  (Read 11345 times)

Offline stevehuckss396

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Re: Hall Sensors
« Reply #15 on: January 18, 2014, 10:54:54 PM »
I plan to buy a cheap magnetic Scotty dog in the toy store to find the North of my magnets, as I tend to lose track.
Mosey


Don't waste your time and money. Just wire it up and flash the sensor to find the correct pole. Then mark the magnet by painting the end with a sharpie. Press them in the disk and be done with it. That way north and south mean nothing. All you have to worry about is "this side fires the plugs" and you are 100% positive it will be correct when assembled.
« Last Edit: January 18, 2014, 10:57:56 PM by stevehuckss396 »
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline Tennessee Whiskey

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Re: Hall Sensors
« Reply #16 on: January 18, 2014, 11:58:04 PM »
And I'm still trying to start a fire with a magnifying glass :lolb: :lolb:. Y'all just keep on, I'm gonna need this info someday, I know I will :ThumbsUp:

Whiskey

Offline Mosey

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Re: Hall Sensors
« Reply #17 on: January 19, 2014, 01:26:49 AM »
I have a couple of quick questions about your great suggestions. Hall sensors have 3 wires, when looking from the side with the beveled edges, from the left  leads 1,2,& 3 go as follows according to Jerry Howells layout: 1. goes I dont know where 2. Goes to Engine Ground,  negative, and 3. goes to 6 volt positive.
If that is correct, do all Hall Sensors have the same 3 leads?
Which do you mean is the Controlled lead, and which is the positive? (the #3?)
Just to amuse you, I include a picture of the board with it's heat sink in place on the engine, and the Roy Sholl dual coil is just above in it's holder.


Mosey


Offline stevehuckss396

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Re: Hall Sensors
« Reply #18 on: January 19, 2014, 02:18:09 AM »
Hard to say without a drawing Mosey but I'm sure all 3 go back to the little blue terminal strip. You would have to look at the schematic for which spot.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline Bezalel

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Re: Hall Sensors
« Reply #19 on: January 19, 2014, 03:21:35 AM »
Hi Mosey


The Bullet is looking good,


I'm curious about the configuration of the thermal connection to the heat sink.
 
Please put me straight if it is not the case, however, it appears to be that the fiberglass PCB is mounted between the the T220 package and the heat sink. This configuration can promote early component failure due to heat stress. The heat transfer to the heat sink through the bolt only, is quite limited.


It is good practice to bolt the thermal connection tab directly to the heat-sink with heat transfer compound between the two.


Fiberglass is not celebrated for it's thermal conductivity properties.


Where electrical isolation is required between the heat sink and the thermal tab of the device a mica insulator with heat sink compound on both sides of the insulator should be used.

This may have nothing to do with the failure discussed in the original question, but it is an important issue when you are looking for heat related semiconductor failure.

Bez
Queensland - wet one day, humid the next

Offline Don1966

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Re: Hall Sensors
« Reply #20 on: January 19, 2014, 03:43:11 AM »
Mosey the the no. 1 lead is positive, the no.2 lead is negative, the no.3 lead is out or controlled lead. Disconnect the Hall leads from the board and touch the terminal on the PCB where no.2 and no .3 leads connected. Just rack a jumper across the two terminal to test your PCB. This will simulate a contact closure. The Hall Sensor makes these two terminals together when it is turned on. If the sensor is shorted the board will stay on. PM if you still have problems.
Bez is correct about the Heat Sink, the transistor should be mounted on it for proper heat transfer. There should of had a flat mica insulator to mount beneath the transistor with the kit. This is to isolate the transistor from the heat sink.

Don
« Last Edit: January 19, 2014, 03:48:14 AM by Don1966 »

Offline Bezalel

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Re: Hall Sensors
« Reply #21 on: January 19, 2014, 04:39:03 AM »
Mosey


I'm not familiar with this particular Circuit so hopefully you and Don can guide my comments with regard to the specifics.

Was a mica insulator supplied? If yes, there would also have to be insulating bushes for the Brass fastener or a nylon bolt and nut.
You already mentioned it worked for a little while so the need for electrical isolation isn't an issue, the inability to dissipate enough heat is a likely cause of the failure.

It looks like electrical isolation between the transistor and the heat sink is not required but if it is, then bolting the transistor to the heat sink with an uninsulated brass (conducting) fastener (as appears to be the case in the photo) is definitively a no go.

Cheers

Bez
Queensland - wet one day, humid the next

Offline Mosey

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Re: Hall Sensors
« Reply #22 on: January 19, 2014, 02:57:13 PM »
Bez,
Howell's instructions shows the heat-sink as "not-absolutely necessary", and only for "unusual circumstances cause it to heat up". He shows it mounted with a 2-56 pan-head screw, thru the transistor, thru the heat-sink, and to the board. "The tab is only for that purpose". So, I used a pretty gold-anodized fluted heat sink from one of my R/C speed controls and mounted it with a brass 2-56 bolt I had lying around. No insulation is called for. This contradicts what you guys are saying, so I will check with Allen Howell to verify this point.
Don,
Can't thank you enough for your explanation of the Hall sensor's lead assignments, now I can run this simple test and get on with it!
I imagine there may be 1 or 2 other guys with as little knowledge as me who could benefit from this discussion, as there is a lot of talk about Hall sensors.
The Roy Sholl dual coil is a major part of this project, so we will see it work when I get the board working.
Thanks to Steve also, Buddy.
Mosey :Doh: :stir: :happyreader:

Offline Mosey

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Re: Hall Sensors
« Reply #23 on: January 19, 2014, 09:37:58 PM »
I did  as suggested by Don, and there is no voltage at the 2 leads, which confirms to me that the transistor is bad. I will replace it and test again. Hopefully, that will do it. I discovered a polarity error in connecting the power,and hope not to repeat that stupid move.
In the future, I will use polarized connectors. :Doh:
Stay tuned. It is important to me to try to solve this myself, even though I have offers of expert help. :hammerbash:
Mosey

fcheslop

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Re: Hall Sensors
« Reply #24 on: January 19, 2014, 10:38:59 PM »
Hi Mosey, Not sure but Iv a niggling feeling about the capacitor mounted on the terminal strip I seem to remember it was for point ignition and not hall switching could well be wrong as my drawings are in the shop but will have a look tomorrow evening.
The output transistor on my version is simply bolted to the heat sink with no insulator and has never been a problem.I blew both the Hall and the output transistor after loosing the engine ground :facepalm:and Iv fitted a larger diode.
I think I bought my TM6 when I bought some drawings from Mr Shores but not sure if I bought it from him it wasnt a kit just a drawing? so I built it on vero board.
Its now ran for several years
Good luck
cheers
frazer
« Last Edit: January 19, 2014, 10:42:31 PM by fcheslop »

Offline Mosey

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Re: Hall Sensors
« Reply #25 on: January 19, 2014, 11:03:27 PM »
The cap came with the coil from Roy Sholls and I installed it. Is it a problem? I thought these coils need a cap to work properly.
Mosey

Offline stevehuckss396

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Re: Hall Sensors
« Reply #26 on: January 19, 2014, 11:14:35 PM »
The cap came with the coil from Roy Sholls and I installed it. Is it a problem? I thought these coils need a cap to work properly.
Mosey

Hey Mosey. If Roy sent it, use it. He does a lot of testing so it's there for a reason. I doubt he would send it if it were not needed.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline Mosey

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Re: Hall Sensors
« Reply #27 on: January 20, 2014, 12:33:31 AM »
Yes, thanks Steve, Roy knows this stuff,  and Caps are mentioned in Bob Shore's book as necessary. Cap is going to stay.
Mosey

Offline Bezalel

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Re: Hall Sensors
« Reply #28 on: January 20, 2014, 01:55:10 AM »
Hi Mosey
 
Good to see your making progress.
 
 
Howell's instructions shows the heat-sink as "not-absolutely necessary", and only for "unusual circumstances cause it to heat up". He shows it mounted with a 2-56 pan-head screw, thru the transistor, thru the heat-sink, and to the board. "The tab is only for that purpose".

I might just mention the real purpose of the tab.
 
Which is to act itself as a heat sink with a large surface area ( mostly the back of the semiconductor) to disipate the heat into the air.
A small part of the surface area is sacrificed  in the form of a hole which can be used to secure the device to a bigger heat sink.
If you bolt one side of the device to a thermal insulator, it can't disipate the heat and Thermal-runaway kicks in - the kryptonite for semiconductors  -
 
These apparently small details do make a difference for semicanductor long life.
 
Howell's design obviously uses the correct size device in the circuit to disipate the heat when the transistor is standing in free air.
Covering part of the heat sink changes the rules and is like turning off the cooling fan.
 
I'm sure we all have an understanding of what happens when the fan stops working in a computer.
 
Bez
 
Queensland - wet one day, humid the next

Offline Don1966

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Re: Hall Sensors
« Reply #29 on: January 20, 2014, 02:12:55 AM »
Yes, thanks Steve, Roy knows this stuff,  and Caps are mentioned in Bob Shore's book as necessary. Cap is going to stay.
Mosey
Roy might have designed has coil around the capacitor. The capacitor and the coil act as a tune circuit to intensify the secondary voltage of the coil. So I would ask Roy if it is. New modern ignition coils no longer need it with electronic switching circuits.

Don