Hall effect sensor

firepong

@dc42 There is no resistor on the board at all for the output. When checking resistance from the output to the sense line wire, it comes up as .1ohm (Basically 0), which made me decide to add a resistor on the sensor line itself. Have some on order that should be the right resistance for the sense line.

dc42

Can you trace the output circuitry, back to one of the transistors? Or get a schematic out of the supplier.

firepong

@dc42 said in Hall effect sensor:

Can you trace the output circuitry, back to one of the transistors? Or get a schematic out of the supplier.

Went ahead and traced out the whole board. This is what it looks like, traces and all. One of the R2 pads with no wire, is going to ground.

alt text

dc42

Thanks. Can you tell me what the top pad of Q2 is connected to, and the right pad of Q2?

I emailed the supplier and received this response:

"The limit sensor will output abut 1.4 volts in the tripped state. To accommodate the output needs of the Duet you can use a voltage divider the bring the sensor out voltage to the necessary level."

This explains the problem, because 1.4V is out of tolerance for any 3.3V electronics and is marginal even for some 5V electronics. It may be that if you connect a 330R or 470R resistor between output and ground, that will bring the voltage level low enough.

firepong

@dc42 said in Hall effect sensor:

Thanks. Can you tell me what the top pad of Q2 is connected to, and the right pad of Q2?

I emailed the supplier and received this response:

"The limit sensor will output abut 1.4 volts in the tripped state. To accommodate the output needs of the Duet you can use a voltage divider the bring the sensor out voltage to the necessary level."

This explains the problem, because 1.4V is out of tolerance for any 3.3V electronics and is marginal even for some 5V electronics. It may be that if you connect a 330R or 470R resistor between output and ground, that will bring the voltage level low enough.

Q1 is going to the positive side of the red LED and Q2 is going to ground. The #2 through-hole point is the only connection to the top of Q1, going to the red LED.
Also, messed up the line that is connecting the green and red LED. That line goes to the bottom right of Q2. Can't believe I messed that up x.x

Here's the new layout:
alt text

dc42

Thanks. Are you able to read any markings on Q1 and Q2?

firepong

@dc42 said in Hall effect sensor:

Thanks. Are you able to read any markings on Q1 and Q2?

They say 2A6 thats all they say sadly x.x

dc42

It looks to me that the Hall sensor is driving the output directly and the transistor are only present to drive the LEDs. Unfortunately, most 3.3V Hall sensors have very low output drive, and are not capable if driving the Duet endstop inputs directly.

When I designed a Hall effect endstop board several years ago, I included a buffer to drive both indication LEDs and the 3D printer controller. It needs just one 5-or 6-pin IC to do that, the same size as just one of the transistors on that board.

Vlad

@dc42 do you guys have those buffers for sale or possibly the whole endstop? Can't make my 3.3V hall sensor work either. Dimly lit LED is what I get. Triggered at 0V, not triggered feeds 1.62V into the board pin.

AndreS

@Vlad as mentioned in your other thread, your 3.3V hall sensor is a linear output type. A buffer circuit will not help. You need a circuit with an comparator and a pot to form a didgital output.