Testing Hall sensors

[ElectricGod]

Since there is a pullup voltage on the hall signal line from the controller (or tester), then a steady voltage can mean either a bad connection from the hall itself to the output pin you're testing (anything from a bad crimp at that pin, to a broken wire anywhere from there to the hall, to the solder joint of that wire on the hall lead), or it can mean a failed hall.

Pull-up voltage? Really? Are you sure? Halls tend to never swing from 0 to supply voltage. I've played with probably 10 different models of linear and digital halls and all of them had a minimum voltage that was more than 0 volts and maximum voltage that was less than supply voltage. Is this perhaps what you are referring to as a pull-up voltage?

Halls used in a motor should swing to their maximum output voltage in the presence of any magnet. Halls are usually powered at something close to 5 volts so I commonly see 4.3 to 4.7 volts max on the signal leg of the hall in the presence of a magnet. If the hall doesn't swing...it is likely bad, but sometimes wire insulation gets split and creates short too. I've popped all 3 of the halls in motor from that happening against the scooter frame. Everything was fine one second and a second later no motor action at all. I thought I burned out the controller and was just 3 cheap halls shorted to the frame. PHEW!

 

[amberwolf]

Since there is a pullup voltage on the hall signal line from the controller (or tester), then a steady voltage can mean either a bad connection from the hall itself to the output pin you're testing (anything from a bad crimp at that pin, to a broken wire anywhere from there to the hall, to the solder joint of that wire on the hall lead), or it can mean a failed hall.

Pull-up voltage? Really? Are you sure? Halls tend to never swing from 0 to supply voltage. I've played with probably 10 different models of linear and digital halls and all of them had a minimum voltage that was more than 0 volts and maximum voltage that was less than supply voltage. Is this perhaps what you are referring to as a pull-up voltage?

Halls used in a motor should swing to their maximum output voltage in the presence of any magnet. Halls are usually powered at something close to 5 volts so I commonly see 4.3 to 4.7 volts max on the signal leg of the hall in the presence of a magnet. If the hall doesn't swing...it is likely bad, but sometimes wire insulation gets split and creates short too. I've popped all 3 of the halls in motor from that happening against the scooter frame. Everything was fine one second and a second later no motor action at all. I thought I burned out the controller and was just 3 cheap halls shorted to the frame. PHEW!

Perhaps some background explanation is necessary:

The halls typically used in ebike motors are some form or clone of the Honeywell SS41A.
http://www.mouser.com/ProductDetail/Honeywell/SS41/?qs=%2Ffq2y7sSKcK%2F%252bhfJuO3wrA%3D%3D

This is a current-sinking-output device. Typically it can sink a few mA.
http://www.mouser.com/ds/2/187/honeywell-sensing-ss40-catalog-page-740399.pdf

That means that it does not output any voltage, it simply sinks current when it is turned on by a magnetic field.

When it is not turned on it is a high resistance output.

Pull up resistors are used inside the controller (or sometimes inside the motor on the hall board, but not very often), which run (usually) from the 5V supply to each of the hall sensor lines. Rarely, they run them from the 12v supply instead.

That provides the actual voltage you see on the hall signal lines, and is why on most motors you will not see any voltage switching (or very little, mV) on the halls if the controller is not connected when you manually spin a motor to check the halls.


Hence the term, "pull up voltage".

 

[ElectricGod]

Since there is a pullup voltage on the hall signal line from the controller (or tester), then a steady voltage can mean either a bad connection from the hall itself to the output pin you're testing (anything from a bad crimp at that pin, to a broken wire anywhere from there to the hall, to the solder joint of that wire on the hall lead), or it can mean a failed hall.

Pull-up voltage? Really? Are you sure? Halls tend to never swing from 0 to supply voltage. I've played with probably 10 different models of linear and digital halls and all of them had a minimum voltage that was more than 0 volts and maximum voltage that was less than supply voltage. Is this perhaps what you are referring to as a pull-up voltage?

Halls used in a motor should swing to their maximum output voltage in the presence of any magnet. Halls are usually powered at something close to 5 volts so I commonly see 4.3 to 4.7 volts max on the signal leg of the hall in the presence of a magnet. If the hall doesn't swing...it is likely bad, but sometimes wire insulation gets split and creates short too. I've popped all 3 of the halls in motor from that happening against the scooter frame. Everything was fine one second and a second later no motor action at all. I thought I burned out the controller and was just 3 cheap halls shorted to the frame. PHEW!

Perhaps some background explanation is necessary:

The halls typically used in ebike motors are some form or clone of the Honeywell SS41A.
http://www.mouser.com/ProductDetail/Honeywell/SS41/?qs=%2Ffq2y7sSKcK%2F%252bhfJuO3wrA%3D%3D

This is a current-sinking-output device. Typically it can sink a few mA.
http://www.mouser.com/ds/2/187/honeywell-sensing-ss40-catalog-page-740399.pdf

That means that it does not output any voltage, it simply sinks current when it is turned on by a magnetic field.

When it is not turned on it is a high resistance output.

Pull up resistors are used inside the controller (or sometimes inside the motor on the hall board, but not very often), which run (usually) from the 5V supply to each of the hall sensor lines. Rarely, they run them from the 12v supply instead.

That provides the actual voltage you see on the hall signal lines, and is why on most motors you will not see any voltage switching (or very little, mV) on the halls if the controller is not connected when you manually spin a motor to check the halls.


Hence the term, "pull up voltage".

Thanks for the info. I thought halls worked exactly opposite of what you said, so I pulled up the spec sheet for the 41F hall and sure enough all the example schematics show a pull up resistor and the hall sinks about 6.8mA.

 

[ElectricGod]

If anyone has read this thread before, I had some incorrect information in the thread and also an incomplete set of pictures. That's all corrected now. I also added a post about what backwards halls look like when tested.

 

[ElectricGod]

I've been saying that halls don't always work correctly so I test all of them before they ever get used in anything. I just pulled out all my backwards SS41F halls to see if they all responded backwards and they did except one. So this post is about that hall. This is exactly why I test every single hall in 3 ways. Bad behavior like this happens from time to time. I just don't trust halls until I test them myself! This hall got tossed in the trash after this. This hall was completely useless for any use at all.

I put the hall in my tester and hit the test button. It tested normal with no magnet present. I instantly thought a good hall got in with the backwards ones. BTW...no magnet always tests as a bipolar transistor.

I then put a north magnet face next to it and retested and it tested as back to back diodes. OK...that's not right. It should display a transistor right now. You can see in the picture that I have the south magnet face away from the hall.

I then placed the south magnet face next to the hall and retested and it tested as a transistor again. WTF?! That ought to be back to back diodes.