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DIY Hall input board

Posted: Sat Nov 09, 2013 1:54 am
by russian
Let's put together a simplest board.

The simplest board would be a board for Hall type wire sniffing - the board would have an LED to blink together with the signal in the wire and it would let us connect the discovery board to the wire running from the Hall sensor to the ECU without disruption.

For this project, we will need:
1) a breadboard
2) some jumper wires: three male-male wires and four male-female wires
3) a LED
4) a resistor to keep the LED alive. LEDs do not like too much current, a typical 5mm led needs 150 Ohm resistor if we are running at 5 volts.
5) a single-supply, rail-to-rail operational amplifier (op-amp). I have used OPA2340 - that's Digikey part no OPA2340PA-ND. Someone should use MCP6002-I/P-ND just to try it, this one is much cheaper.

We will be using only channel B of this dual-channel amplifier.

On the picture, the black wire is ground - that's pin 4 of the chip (pins are counted anti-clockwise starting from the circle mark on the plastic)
The green wire is input, it's where the hall sensor wire is connected. This green wire is connected to pin 5 of the op-amp chip.
One of the yellow wires goes from pin 6 on the op-amp to the PC6 pin on the discovery board. Another yellow wire connects pin 5 to pin 6, that's the voodoo magic of op-amps.
The red wire supplies the op-amp though pin 8.

The resistor goes from pin 7 to the longer lead of the LED. The longer lead of the LED is called anode but that's not really important :)
The short lead of the LED is ground.

We are expecting the LED to blink with the signal - it should be obvious blinking at idle and faster blinking if you rev it.

Image

Tomorrow I will draw the schematic and that would make everything much more simple :) That's in case no one would publish this schematic before I do.

Re: DIY Hall input board

Posted: Sun Nov 10, 2013 2:21 pm
by russian
There is a number of great reference sheets at http://www.akafugu.jp/resources/
Worth posting here I think

Image

Re: DIY Hall input board

Posted: Mon Nov 11, 2013 5:00 pm
by russian
Here is how it should look when you get everything together


Re: DIY Hall input board

Posted: Tue Nov 12, 2013 12:29 pm
by skeeters_keeper
OPA2340 - that's Digikey part no OPA2340PA-ND. Someone should use MCP6002-I/P-ND just to try it, this one is much cheaper.
The MCP6002 is 1Mhz and the OPA is 5.5Mhz - is the MCP going to be fast enough? There are a few other differences too (input current etc) - and I don't know enough about how its being used yet to know if that's going to matter. If these should work I'm going to order a few, and probably 1-2 of the OPA2340s as well just incase they end up not working.

Re: DIY Hall input board

Posted: Tue Nov 12, 2013 12:39 pm
by russian
skeeters_keeper wrote:The MCP6002 is 1Mhz and the OPA is 5.5Mhz
Our engine is 1Khz tops. I think 1Mhz or 5Mhz would not do the difference, especially for slower applications like coolant temp and even throttle position.

If would be great if you can order a couple of both, compare and tell us if you have noticed any difference.

Re: DIY Hall input board

Posted: Tue Nov 12, 2013 5:49 pm
by skeeters_keeper
OK. I ordered 10 of the MCP6002 and one of the others so I have something to compare against.

Re: DIY Hall input board

Posted: Thu Nov 14, 2013 2:00 am
by russian
Finally the schematic

Image

There is a bit of flexibility on the resistor - while 1K is recommended, 150Ohm and anything in between would work also.

Re: DIY Hall input board

Posted: Sun Jan 05, 2014 1:13 pm
by hasse.69

Re: DIY Hall input board

Posted: Sun Jul 15, 2018 12:56 pm
by Yaban
Maybe it's newbie question but why you need a opamp to enter a hall sensor in a ecu io pin ? A pullup resistor is not enough with rusefi ?
Can you explain the reason.
Thank you

Re: DIY Hall input board

Posted: Mon Jul 16, 2018 1:04 am
by kb1gtt
Op-amp circuit is a generic input buffer. You can do it with out the op-amp. However the Frankenso's inputs allow far more than just a hall sensor.

Re: DIY Hall input board

Posted: Mon Jul 16, 2018 10:38 am
by Yaban
Basically im megasquirt experienced that's why I don't understand well what is the philosophy of rusefi hardware. An io pin for trigger input need two informations basically. 1 or 0. Hall sensor mostly switch to the ground need a pull up resistor.....
Vr sensor the most easily way I've find is lm1815 vr conditioner.... That also switch to the ground with a pullup resistor....
I hardly understand why you use all the places opamp for dealing with sensor that mostly are just variable resistor or 1-0 switch signals.
Noise filtering or just to adapt 5v circuit with 3.3v mcu ?