Help with DIY loadcell for T3PA

[tarheel]

Hi

I was searching into a upgrade of my t3pa, a cheap upgrade, and seeing this tutorial, i decided to try. The instruction are simple and basics. I bought all of it, the loadcell, the amp from leo bodnar and so. But i cant receive any response from de LC. The signal doesnt show on control panel at all. I tried so many combinations of wiring but nothing. I rebought a new LC just in case the previous was broken, but i still keep same at the problem.

Anyone that had a LC at this style can help me to understant what h**l is going on?

Ty

 

[Panicpete]

I dont't have the t3pa pedals or a four-wire load cell, but i have modded my Logitech Pedals with two three-wire load cells and have read quite a bit about load cells, so maybe I can help.

To check everything you will need a Multimeter and a ~5V power supply.
You can measure the resistance between the following wires of the load cell:
Black - White
Black - Green
Red - White
Red - Green
The resistance should be roughly the same for all measurements. If not, the load cell itself is probably faulty.

Next, you can measure the resistance between Red - White and Black - Green while applying a varying force to the load cell. The resistance should change slightly when force is applied (if not, check the other way round, so Red - Green and Black - White and swap the White and Green wires in the following paragraph accordingly).

If everything looks good so far, connect the load cell to the amplifier. According the the information in this thread, Black wire is GND, Red wire is +5V, White is -IN and Green is +IN. Connect the amplifier to your 5V power source and measure the voltage between the GND and OUT pin of the amplifier. With no force applied to the load cell, you should have 0V, increasing when force is applied.

If that is also OK, check the pin configuration of the connector in your pedals. In the thread you linked, the guy mentioned that in the picture ha had it the wrong way round, so you should get either +3,3V or +5V when connecting the negative(black) wire of your multimeter to the right pin and positive(red) wire to the left pin (with the pedals plugged in and amplifier not connected).
Connect your amplifier accordingly and check again if it works.

If anything is not as expected please reply here and we can try to find out what the problem is.

 

[tarheel]

I dont't have the t3pa pedals or a four-wire load cell, but i have modded my Logitech Pedals with two three-wire load cells and have read quite a bit about load cells, so maybe I can help.

To check everything you will need a Multimeter and a ~5V power supply.
You can measure the resistance between the following wires of the load cell:
Black - White
Black - Green
Red - White
Red - Green
The resistance should be roughly the same for all measurements. If not, the load cell itself is probably faulty.

Next, you can measure the resistance between Red - White and Black - Green while applying a varying force to the load cell. The resistance should change slightly when force is applied (if not, check the other way round, so Red - Green and Black - White and swap the White and Green wires in the following paragraph accordingly).

If everything looks good so far, connect the load cell to the amplifier. According the the information in this thread, Black wire is GND, Red wire is +5V, White is -IN and Green is +IN. Connect the amplifier to your 5V power source and measure the voltage between the GND and OUT pin of the amplifier. With no force applied to the load cell, you should have 0V, increasing when force is applied.

If that is also OK, check the pin configuration of the connector in your pedals. In the thread you linked, the guy mentioned that in the picture ha had it the wrong way round, so you should get either +3,3V or +5V when connecting the negative(black) wire of your multimeter to the right pin and positive(red) wire to the left pin (with the pedals plugged in and amplifier not connected).
Connect your amplifier accordingly and check again if it works.

If anything is not as expected please reply here and we can try to find out what the problem is.

Oh thank so much for your reply.

Well, i had clear al about wiring after my first attempt, but anyway i tried other combinations....But yes, it's like you said. Finally yesterday could solve my problem. The thing is (i think) that is neccesary to close/open your control panel and plug/unplug the conector in the wheel to LC being recognised... I don't know, but i think i did all this with my first LC, so maybe this one was really broken. I don't own a multimeter so i couldnt check that.

Anyway, this run smooth right now, about 40€ total cost. Maybe not worth compared to a simple commercial external LC

Surely your explanation reply solve so many doubts to who try this solution. Ty

 

[Panicpete]

Glad it works now.
Yes it is possible that you have to reconnect the pedals when you change the wiring for it to work. To be sure, I would recommend to have the pedals unplugged completely while making changes to the wiring.

I also found that with my Logitech pedals it can cause problems if you first connect the power supply before making the USB connection. I always make sure to connect USB first and then power. Not sure if this applies to Thrustmaster as well.

 

[senrab51]

Here are a couple of links that might help you figure things out Tarheel is correct you need a multimeter digital is a must.

A good reference site:

Lesson - Working with Load-Cells

Really nice work. :thumbs I have many loadcells laying around as replacement for Fanatec Break pedal. So I have a question. In the pedal thread you...

www.xsimulator.net

Tutorial - DIY load cell brake pedal (short tuto)

Take an unused bathroom scale @10€ or buy load-cells at eBay [ATTACH] you got this piece : [ATTACH] You need 2 load-cells to make a wheatstone bridge...

www.xsimulator.net

Getting Started with Load Cells - SparkFun Learn

Pretty deep tekkie

Wheatstone Bridge - Load Cell Manufacture

Wheatstone Bridge technical specifications and infomation.

www.transducertechniques.com

 

[CRMS]

I'm doing this mod. I bought the Bodnar LCAMP, input could be 2 mv/V as spec just has 1mV/V .. 3mV/V, and a 20kg YZC-133 load cell, output 1mv/V. Just connected up loadcell/LCAMP at 5v from USB and hung weights off it up to 25kg. Zero load is 112mv out from Bodnar, and linear output up to 3528 mv at 25.3kg. Not sure what I should expect as Bodnar data indicates 0 - 4.9v output. Any ideas would be appreciated???

Bodnar LCAMP specs:
Supply voltage (to +5V pin): 5V ± 20%
Output range (on OUT pin): 0 .. 4.9V
Input range (on +IN/-IN terminals): 0 .. +10mV (uni-directional version), -10mV .. +10mV (bi-directional version)
Specified load cell output: 1mV/V .. 3mV/V
Specified load cell excitation voltage: 5V or higher*

YZC-133 specs:
Rated Load: 20Kg
Rated Output: 1.0 ±0.15mV/V
Zero Output: ±0.1mV/V
Cree: 0.03%F.S./30min
Input End: Red+, Black-
Output End: Green+, White-
Input Impedance: 1115±10% Ω

 

[GeekyDeaks]

I have not used the Bodnar, but I have built my own amplifier so I may be able to offer some suggestions on troubleshooting in general, but not specifically with the Bodnar.

Looking at the specs of your LC, I can see that it is rated approx 1mV/V, which I'm assuming is at it's max rated load of 20kg. If you are supplying 5v, then you should be getting a difference of 5mV across the -in/+in at 20kg. 5mV looks to be about 1/2 the range of the Bodnar (0mV - 10mV), so that should mean you getting about 2.5V at 20kg. Looking at your chart, I can see that you are about 2.75V, which is within 10% tolerance and the LC has a tolerance of +/-15%, so that seems within bounds.

If you have an AVO with enough accuracy, I'd be inclined to measure the difference between -in/+in and check it's in spec and also measure the supply to the load cell.

 

[nuno8210]

Hi GeekyDeaks. Did you build your own amplifier? Can you share a tutorial or some schematics and a parts list to buy?
Thanks.

 

[GeekyDeaks]

Hi GeekyDeaks. Did you build your own amplifier? Can you share a tutorial or some schematics and a parts list to buy?
Thanks.

Yeah, I got most of the details on my github page here: https://github.com/GeekyDeaks/g29-load-cell

One thing to note, the circuit is designed to invert the signal, but it was also designed to allow 1 or 2 load cells since I was playing with both configurations and decided to make a single circuit that could be used with either.