Mjoy and load cell

I am in the middle of building pedals for my simulator. I have ordered Leo Bodnar's BU0836-LC board. LC stands for load cell version that has a load cell amplifier on board. To make a long story short I ordered it over a month ago and I still don't have it and Leo will not return any of my emails asking about it. So I am wanting to build a Mjoy16 board and figure out what it takes to hook up my load cell to it. Does anyone have a schematic on the load cell amplifier? I guess I'm off to find the latest Mjoy16 schematic.

Orion

My order from Leo was lost too last year. He didn't answer back either right way, but when I made him some more order for BU0836, he sent me the extra one that was lost! That was so kind!

Oh... I almost forgot... here is a simple Load Cell amplifier circuit: http://www.jamesyawn.com/electronicstan ... oard2.html

What kind of load cell is it? I think an adjustable op-amp circuit would be easy enough to use.

You could also use pressure sensitive resistors without extra circuits:
http://www.sparkfun.com/products/9375

I think he is talking about that kind of load cells.... http://aeroconsystems.com/cart/products ... -20-4.html

Are there any FSRs with higher measuring range available?

10kg FSR wouldnt cut it. Braking pedal forces are up to 100kg without brake booster for full brake.

regards

I don't know if they have them in such a high range, they probably wouldn't last for a long time.

Don't forget, the 10kg range refers to pressure/area. It works out to 10kg/4cm^2 = 2.5kg/cm^2 evenly distributed over the 0.5 diameter area.
Theoretically if you distribute the 100kg force over a 40cm^2 area, the sensor will still see 2.5kg/cm^2, but now we need 100kg force to make it's resistance the same.

I picture a round 40cm^2 round plate, 4cm^2 sensor in the middle. Put a rubber mat on top to give a plush feeling and some travel for modulation, and an other 40cm^2 round plate on top to distribute the force evenly. Mount the pedals on the top plate.

This is of course only in theory, I would love to test it and see how it works out.

The load cell I have can be found on this website. It is the 30kg model.

http://www.elane.net/index.php?go=load_cell

I guess the question should be what circuit would it take to hook this load cell to the mjoy16 that frakk has designed.

Orion

As I posted before this circuit works for your load cell!! Its for rocket base load cells but its the same thing! The amplifier is used for that kind of cells like the one on your link! http://www.jamesyawn.com/electronicstan ... oard2.html

:thbup:



You connect the Dataq-ch1 to an analog input of Mjoy and Dataq-Gnd to the Ground of Mjoy... its not rocket science!!! :lol:

I see that this is using two 9 volt batteries in series as an 18 volt power supply. Do you know the current draw from this? I would like to have it powered by a wall wart type supply but I need to know the power consumption to get the correct model.

I see that this is using two 9 volt batteries in series as an 18 volt power supply. Do you know the current draw from this? I would like to have it powered by a wall wart type supply but I need to know the power consumption to get the correct model.

From the datasheet of INA125:
A single external resistor sets any gain from 4 to
10,000. The INA125 is laser-trimmed for low offset
voltage (250µV), low offset drift (2µV/°C), and high
common-mode rejection (100dB at G = 100). It operates on single (+2.7V to +36V) or dual (±1.35V to
±18V) supplies.
The voltage reference is externally adjustable with pinselectable voltages of 2.5V, 5V, or 10V, allowing use
with a variety of transducers.

So you can power it from single source +5v and set the reference voltage to +5v also... Do you need me to draw you new circuit on how to do this? :

There is something similar here http://www.hux.net.au/?p=89
It is from the topic DIY H-Shifter by Willynovi - WIP but Andrew's work.
[img600px]http://www.hux.net.au/wp-content/uploads/2010/03/p3210026_sml1.jpg[/img600px]

Is there a parts list for the mjoy16 like there is for the circuit tronicgr listed above? That list was very useful to me and I appreciate the information.

That site is exactly what I need to be reading. Thanks for that. You guys rock!

Orion

My load cell has a 1.74mv/V output. How do I calculate the resistor size for the gain? My thought is that 2mv/V you need 400 ohm... so a 1.74mv/v would need 348 ohm resistor to get the same gain. Is that correct?

Orion

Anyone looking for cheap load cells??? :brows:

http://www.sparkfun.com/products/10245

:happy:

That is a nice find but it only has three wires coming out so I would guess it is only half of the wheatstone so it won't be as accurate as the ones with a full wheatstone bridge.

Orion

I am digging through the mjoy16 thread and I finally figured out there is two different projects listed. One of which is the atmega8 and the other being the atmega16. I have decided to follow the path of the atmega16. From what I can tell the most recent build is the one dated 11-6-2009. http://www.x-simulator.de/forum/mjoy16-usb-avr-joystick-t726-70.html Is this correct? I really need to know so I can go shopping for parts.

Orion

I placed an order for all the parts to build the load cell amp and the mjoy16. I can't wait to get it all in and start playing... I mean learning how to do this.

Orion