Load Cell not Working

[zapz]

I have a Leo Bodnar load cell amp (click here) (http://www.leobodnar.com/products/BU0836-LC/) and a load cell (click here) (http://parcelscale.com/loadcell/30kg_load_cell.php)

It's all connected as described in the picture (here) (http://www.leobodnar.com/products/BU0836-LC/LCwires.jpg)

However I'm not getting any signal to the PC, any ideas? The analog inputs on Leo's board are working fine, it's just the load cell that's not giving a signal...

[Niels_at_home]

can you show a picture of how you've mounted it all in your pedals?

[jeroenvdb]

Check the mounting of the loadcell.
Is the force applied in the right direction?

Build a wheatstone bridge circuit to replace the loadcell.
out
|
+-r1-p1---+
| |
in-+ +-in
| |
+-r1-+-r2-+
|
out
r1 is 10kΩ resistor, r2 a 20Ω resistor and p1 a 20Ω pot
See if you get a signal now and if you can vary it with the pot.

Do you have a multimeter to do some tests with?
1st:
Measure the resistance over each of the loadcell's wires.
It should not be very very high (open circuit) and roughly the same for each pair of wires
2nd:
Apply a voltage over the input wires.
Measure the voltage over the output wires as you vary the force on the loadcell.
It should change with the force and be a few millivolts.

[zapz]

Wow, thanks for the info jeroenvdb. Time to break out the bread board & multi meter and make a trip to Radio Shack. :-)

Niels at Home - These are existing DIY pedals that I'm retro fitting with a load cell (which is not currently mounted). It's a 30Kg LC and I'm trying to flex it (by hand) in the right direction to verify it works, but it's not registering any force. BTW I remember your user name from the DIY forum over at RSC circa 2004. :thumbup:

[Niels_at_home]

You can't really test it this way because it doesn't respond to bending, you really have to clamp one end to the edge of a desk (use a glue clamp for example) and press on the other end downwards. I never really managed to get a real readout trying to press it by hand..

I bet it all works fine! :)

[zapz]

That good to know thanks Niels. I'll test it out with one end clamped down and see what happens.

[zapz]

Well unfortunately there's still no output from the LC/LC amp when I clamped it down and applied ample force.

[jeroenvdb]

Does it work if you apply force in the opposite direction or swap the output wires?

[zapz]

Do you have a multimeter to do some tests with?
1st:
Measure the resistance over each of the loadcell's wires.
It should not be very very high (open circuit) and roughly the same for each pair of wires


From gnd to:

in+ I get 6K ohms
in- I get 200 ohms
5V I get 250 ohms

From in+ to in- I get 7K ohms



2nd:
Apply a voltage over the input wires.
Measure the voltage over the output wires as you vary the force on the loadcell.
It should change with the force and be a few millivolts.

When applying 5V to the +in I get no output voltage at all on in-.

So I guess this tell us that the load cell is Kaput, right?

[zapz]

Does it work if you apply force in the opposite direction or swap the output wires?

Thanks for the suggestion, I'll give it a try and report back.

[edit] - still not working with force applied in either direction

[jeroenvdb]

Those resistances look odd.
They should be symmetrical.
200 ohms sounds too low to me, mine has resistances of a about 400 ohms.

What kind of voltage do you get on the output if you feed the loadcell with a battery and apply force?

[zapz]

Those resistances look odd.
They should be symmetrical.
200 ohms sounds too low to me, mine has resistances of a about 400 ohms.

What kind of voltage do you get on the output if you feed the loadcell with a battery and apply force?

I'll can try to hook it up to a battery, but I know that Leo's board is supplying it with 5v and I'm not getting any output from that...

The LC manufacturer is claiming that I have miss wired the load cell, but so far has not supplied me the information for the correct wiring.

[zapz]

OK I finally figured out the issue. The LC was miss wired, but unfortunately neither the LC manufacture or Mr Bodnar's suggested wiring was correct.

An educated guess finally worked:

(LC amp) (Load Cell)
gnd white and clear
in+ red
in- blk
5V green

[Derek Speare]

I'm late to the party, but use this diagram from Elane - that's the source for LC's:

http://www.elane.net/images/Todd_cannon_lc_big.jpg

[zapz]

I'm late to the party, but use this diagram from Elane - that's the source for LC's:

Thanks DeeMoNay. Elan referred me to the same diagram... perhaps I'm missing something, but

(1) The Elane LC has 5 wires, not just the 4 mention in the diagram. The 5th wire (clear) is a shield that connects to ground.

(2) The inputs on Leo's LC amp are labeled (gnd) (in+) (in-) (5v) which at least to me does not correlate to Elans LC labels of (S-) (S+) (E-) (E+).

Anyway I've figured it out and it's all working great. The load cell is so much better than the progressive spring and pot I was using before.

[Derek Speare]

Thanks DeeMoNay. Elan referred me to the same diagram... perhaps I'm missing something, but

(1) The Elane LC has 5 wires, not just the 4 mention in the diagram. The 5th wire (clear) is a shield that connects to ground.

(2) The inputs on Leo's LC amp are labeled (gnd) (in+) (in-) (5v) which at least to me does not correlate to Elans LC labels of (S-) (S+) (E-) (E+).

Anyway I've figured it out and it's all working great. The load cell is so much better than the progressive spring and pot I was using before.

Can you show how you connected it and indicate where (S-) (S+) (E-) (E+) connect on the Leo board?

I think it goes:

LEO -> LoadCell
(+5V) -> (E+) red
(gnd) -> (E-) black
(in+) -> (S+) green
(in-) -> (S-) white

It's unusual that Elane doesn't say anything about the clear wire. I'd really appreciate knowing how you connected it. :)

d

[zapz]

No worries, this is how I have it connected.

(LC amp)........(Load Cell)
gnd__________white and clear (S-)
in+___________red (E+)
in-___________blk (E-)
5V___________green (S+)

[Derek Speare]

No worries, this is how I have it connected.

(LC amp)........(Load Cell)
gnd__________white and clear (S-)
in+___________red (E+)
in-___________blk (E-)
5V___________green (S+)

Thanks muchly :thumbup::thumbup:

d

[jeroenvdb]

E=, E-, S+ and S- are the corners of the loadcell's wheatstone bridge.
http://i.imgur.com/atUpp.jpg
One pair needs to be fed with a fixed voltage and the voltage over the other pair is read as the output.
You can swap the E and S pairs and the bridge will still work.
If you swap the + and - of a pair the response of the bridge will be inverted.

[Syaitann]

Sorry to hijack an old thread but this thread is most relevant to my problem.
Picked up Leo Bodnar LC Amp + LC. Got it working immediately but the output was reversed, fully depressed 0%, released 100% in game control. Read up this thread mentioning reversing a pair, I tried that and a few other combination but still no go.

Combination that I did:

GND -IN +IN +5v (amp)
blk wht grn red (from lc, 1st attempt. functioning but reversed)
blk grn wht red (spiked once when depressing pedal, then no detection. full press, full release nothing happened)
red grn wht blk - reversed
red wht grn blk - nothing
wht blk red grn - reversed
wht red blk grn - nothing
grn red blk wht - reversed
grn blk red wht - nothing

Help anyone

edit: forgot to mention, this is direct to G25. also in Leo's site he warned about correct +5v and gnd connection on pot side, so i'm a bit apprehensive wanting to swap em.

[Line Out]

Hello everyone. I'm new here, and there is a set of T500 RS and A TH8RS coming to my way in a few weeks (I hope) and been thinking of doing a DIY load cell mod on the brake pedal.

So, do I need anything else than a Bodnar Standalone Load Cell Amplifier (http://www.leobodnar.com/products/LC-amp/) and a Load Cell (http://www.zemic.nl/Products-Single-Point-load-cells/product-l6d-load-cell.html)?

I've enquired the price of a ZEMIC L6D 30Kg Load cell Datasheet (http://www.zemic.nl/media/L6D_Datasheet.pdf)

I was thinking of making the mod similar to the jbodin's BLC-T500RS in regards of the construction, as it seems very simple.

[Line Out]

Anyone?

[jeroenvdb]

Yes, that is all you need.
If you want to change the response of the loadcell/amplifier then you can change the resistors on the board.