Bad hall sensor and throttle voltages

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420b   100 W

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 16 2018 3:47pm

Well I pulled out the 7805 and ran 5v through it (data sheet says up to 30v is ok) and it’s producing 2.6v. Then when I ran 3.3v through it it’s producing 1.1v. So it seems like this thing is dead.

420b   100 W

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 16 2018 3:51pm

fechter wrote:
Aug 16 2018 3:31pm
If you only have 1v on the input, then the problem is most likely upstream. There is a 12v regulator that typically feeds the 78L05. I couldn't really see well in the pictures but check out the little 8 legged chip close to the 78L05 and see if you can read the number. Most of the newer controllers are using switching regulators for the 12v. Once we have a number, we can try to look it up and get a datasheet that shows which pin is doing what. Usually when those switcher chips go bad, they smoke. Possibly there's a part feeding that went bad or the inductor went open.
Yes there is an 8 pin A42S BBHQ. I did try to find a data sheet to no avail. I’d mention that 5v output of the 7805 goes to a resistor and to that chip it seems. So maybe bad 7805 killed that.

Also that 8 pin goes into the 5v regulator input.

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 16 2018 3:54pm

So can I give it some external 5v from a power supply in place of the 7805?

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 16 2018 4:10pm

My throttle hall sensor works fine when I put 5 volts through it. I can’t get the controller to work even if I give it 5 volts. So I think I just shall replace the controller. Bummer.

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 16 2018 5:43pm

frock YES!!!!! I had the 5 volt on the wrong way, because the outline on the board showed it reversed. Never have I had my foot run over by a bike and been this happy about it! Just need a new 7805 and I’m good to go! THANK YOU SO MUCH fetcher and amberwolf!!!

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 22 2018 6:51pm

So I bought these but seems like theyre the wrong tool for the job. https://www.mouser.com/datasheet/2/389/l78-974043.pdf

Absolute max is 35v first of all, which is lower than my battery. Secondly when I plug it into my breadboard with 5v input it gets too hot to touch after a few seconds. WTF?

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fechter   100 GW

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Re: Bad hall sensor and throttle voltages

Post by fechter » Aug 22 2018 9:17pm

Normally the input would be getting around 12v from another regulator on the board. Without the 7805 installed, you should be able to measure this when the power is on. If you see pack voltage, then you have more problems upstream.
"One test is worth a thousand opinions"

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 23 2018 7:48pm

The issue was that I reversed polarity to the 7805. Anyways, i realized while trying to solve the heat issue that the 7805 is extremely inefficient. I require about a 30v drop from 35v to 5v at 300mA for hall sensors, which is 9 watts of lost power to heat. So wow, what a waste!

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Re: Bad hall sensor and throttle voltages

Post by fechter » Aug 23 2018 11:19pm

300mA is way more than the hall sensors should take. Most controllers use under 100mA on the 5v line. That's still a lot of wasted heat though. The newer designs are all using switching regulators that generate much less heat. If you have room, you can get one of those cheap adjustable regulator boards. I have used several of them with good results. Just run wires to the holes on the board.

Here's an example: https://www.ebay.com/itm/Lot-LM2596S-DC ... 0869636683
"One test is worth a thousand opinions"

420b   100 W

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Re: Bad hall sensor and throttle voltages

Post by 420b » Aug 25 2018 11:08am

fechter wrote:
Aug 23 2018 11:19pm
300mA is way more than the hall sensors should take. Most controllers use under 100mA on the 5v line. That's still a lot of wasted heat though. The newer designs are all using switching regulators that generate much less heat. If you have room, you can get one of those cheap adjustable regulator boards. I have used several of them with good results. Just run wires to the holes on the board.

Here's an example: https://www.ebay.com/itm/Lot-LM2596S-DC ... 0869636683
Yeah, I bought one of those. I should have room. For now I’m utilizing the switching step up converter on a USB battery pack.

420b   100 W

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Re: Bad hall sensor and throttle voltages

Post by 420b » Sep 02 2018 9:53pm

fechter wrote:
Aug 23 2018 11:19pm
300mA is way more than the hall sensors should take. Most controllers use under 100mA on the 5v line. That's still a lot of wasted heat though. The newer designs are all using switching regulators that generate much less heat. If you have room, you can get one of those cheap adjustable regulator boards. I have used several of them with good results. Just run wires to the holes on the board.

Here's an example: https://www.ebay.com/itm/Lot-LM2596S-DC ... 0869636683
Bought that thing, waited, then blew it up. The marking on the PCB for the 7805 is actually reversed, so I keep getting confused. On the lm2596 that design is actually insulated, but I think it’s fine to connect the negatives to each other. Now I bought one of these: https://rover.ebay.com/rover/0/0/0?mpre ... 2675267612. Looks promising!

420b   100 W

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Re: Bad hall sensor and throttle voltages

Post by 420b » Sep 04 2018 1:32am

fechter wrote:
Aug 23 2018 11:19pm
300mA is way more than the hall sensors should take. Most controllers use under 100mA on the 5v line. That's still a lot of wasted heat though. The newer designs are all using switching regulators that generate much less heat. If you have room, you can get one of those cheap adjustable regulator boards. I have used several of them with good results. Just run wires to the holes on the board.

Here's an example: https://www.ebay.com/itm/Lot-LM2596S-DC ... 0869636683
Oh, the 300mA number was wrong. That was the total 12v supply current. The 12v supply is created using a parallel 160 ohm resistor package which drops 26v at .325mA. The resistor package is really inefficient from my calculations and from my finger actually touching it. I measured it and it’s reaching 160C outside the case. Not good, I’ll have to put in a buck converter I think.

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