MS3X VR Board for VSS Inputs

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MS3X VR Board for VSS Inputs

Postby zguy360 » Fri Aug 19, 2016 2:57 pm

I have read through all of the posts on your forum and an not sure that I have found my answer. I am currently building a V3 board with the MS3X expansion. I will be running the most recent firmware when I get to that point. The existing MS VR inputs are both being used for the crank sensor and the cam sensor.

I would like to use the dual VR board for two VR vehicle speed inputs (sensor in the trans and one wheel speed sensor). From the MS manual, the suggested inputs are on the expansion board and they can only be used for hall effect, without a suitable interface circuit to convert the signal. I have purchased the internal version of your board for this purpose.

My question is, how do I connect your board to these circuits? I would like to keep the VR board mounted inside of the case and would like to keep the wiring internal to the case. Thanks for your help!
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Re: MS3X VR Board for VSS Inputs

Postby jbelanger » Fri Aug 19, 2016 7:06 pm

Unfortunately there is no quick and easy way to do it. The best would be to connect the dual VR board outputs to either the JP2 header on the MS3 card or the JP1 header on the MS3X card. Or you could do small "surgery" on the cable and redirect the corresponding wire(s) to the dual VR board.

With the internal version of the board which is powered from the MS 5V source, you don't need the circuits on the MS3X card. The above would simply bypass the MS3 card. Of course, you still need to connect the VR sensors to the dual VR board inputs in some way; this either requires its own connector or using some free/spare pins on the main board DB37 (or DB15 if you have the 3.57 board).

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Re: MS3X VR Board for VSS Inputs

Postby dontz125 » Sat Aug 20, 2016 1:22 am

Looking in the TS menu, there are a few options for VSS1 & 2 that connect to the JS header on the main board - JS4/5 (ADC7/6), JS7 (PE0), JS10 & JS11, and JS12 (PE1) on a V3.57 board. No additional components are needed - the VR board IS the proctective / adaptive circuitry.
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Re: MS3X VR Board for VSS Inputs

Postby jbelanger » Sat Aug 20, 2016 12:18 pm

That's a good point. I hadn't checked the possible inputs but since you can simply ignore the MS3X and use the main board inputs, that would be a much easier way to go. Simply use spare connector pins for the dual VR board inputs as mentioned in my previous post and connect the outputs to any of the available JS header pads. And don't forget to power the dual VR board (5V and ground) from the main board.

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Re: MS3X VR Board for VSS Inputs

Postby zguy360 » Sun Aug 21, 2016 12:04 am

Thank you all for the help. I do have spare JS inputs that are available, so this makes the most sense. For bringing VR+ and VR- out, do I have to connect both directly to the sensor? For the built in VR inputs on the megasquirt, the ground side of the sensor is just grounded on one of the available ground pins on the db37 connector. Can I do the same with my VSS sensors and jumper the VR- to the internal ground on the proto area?
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Re: MS3X VR Board for VSS Inputs

Postby jbelanger » Sun Aug 21, 2016 12:11 am

You really want to connect VR+ and VR- directly to the sensor and nothing else (besides a connector along the way, of course). Using ground is a last resort and will give away a lot of the potential benefits of the chip on the dual VR board for handling noise and other signal characteristics.

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