G25 g27 diy brake load cell for $75

Edit 8/31, see edit 8/31 in Bold below.


Hello everybody!

I got really sick of a Potentiometer based brake pedal about a month ago and have been research Load Cell mods.

Apelectrix is a reasonable price at $75, but I understand there is very little pedal travel and he hasn't responded to any of my emails anyways.
http://www.apelectrix.com/

Ricmotech is a good load cell mod with great reviews but it is very overpriced in my opinion at $129. Additionally, the spring and damper made of stiff hose I've read has a high preload and feels springy and unnatural.
http://www.ricmotech.com/Load_Cell_Upgrade_Kit_for_Logitech_G25_G27_Pedals_p/rmt-lc27.htm

So after some time I found a site where a guy did his own DIY load cell. What he did is significantly different then what I am planning to do. I will post his article on what he did at the end.

So, lets start with parts needed:

50 KG Button Load Cell - $45

Its 25 MM wide. I have not measured the diameter of the Brake pedal spring cartridge but I believe this will fit.

http://www.robotshop.com/en/button-...2GBRDLDzM4tPkTRUeCB--bwzFNlkaobtyIaAqnw8P8HAQ

Load Cell Amplifier from Leo Bodnar - $15 - You can probably make this yourself if you are an electronics guru


http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=199

"Real Pedal" Spring and Damper upgrade from Ebay - $25


http://www.ebay.com/itm/REAL-PEDAL-...l-brake-mod-/400974876857?hash=item5d5bf710b9

Cable with 3 pin connector - $2.30

http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=202

Tools needed:

Ruler/measuring tape

Drill and drill bit(about 3/16 inch or 5 MM).

Needle nose pliers.

Small hack saw or dremel tool.

Phillips screwdriver #1 and #2.

2.5 MM Allen Wrench

Snips/dikes.

Soldering iron and solder or very small butt connectors and crimping tool.

Zip ties.

That's it for now. There is an installation video on the Ricmotech site. This will be almost the same. I will update in the future. I believe most of you can figure out how this all comes together.

Here is the original article I found. He used a beam load cell, connected directly to the pedal, and mounted a wooden brake pedal to it.

https://chippedwood.wordpress.com/2015/07/07/46/


Edit 8/31

This Sparkfun (US) HX711 Load Cell Amp (10$) should work as well. It puts out a digital signal, and analog, which is what I need. I don't understand how to wire it properly yet. This board will require soldering.

https://www.sparkfun.com/products/13230


Additionally, I recently learned that if you connect your pedals to a separate joystick controller and then to your PC instead of going through your wheel it will increase resolution of your load cell and other potentiometers in the pedals.

Leo Bodnar (UK) makes a cable for G25/G27/DFGT/DFP pedals ($36). It has a joystick controller in it that provides 10 Bit Resolution which is 1024 steps for each axis.
http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=187

They also make a 10 Bit, 12 Bit, and 12 Bit controller with Load Cell Amp. 12 Bit provides 4096 steps per axis. The 12 Bit with Load Cell Amp is $41.
http://www.leobodnar.com/products/BU0836-LC/



Additionally, Derek Speare Designs (US) makes a 12 Bit Joystick Controller with Load Cell Amp. Two versions. One has an adjustable Gain and the cost is $50. The one without adjustable gain is $40. What the heck is adjustable gain?
"Why variable gain? It's simple. You can adjust the sensitivity of your load cell and still maximize your braking channel bandwidth. If you have 4096 steps of resolution, why waste half of it by using a fixed gain amp? The DSD 12bit board with integrated amp lets you use every step you're paying for! (you receive an adjustment knob with the 12bit board using integrated load cell amplifier)."

So, for example if you have a 50KG load cell, and with a fixed gain AMP, you end up using a maximum pressure of 25KG (because that is what is comfortable for you), you end up using half the 4096 resolution; so 2048. With the variable gain, you can increase the gain so that 25KG of pressure is full 4096 resolution.

http://www.derekspearedesigns.com/12-bit-controllers.html




Also, I thought of another, cheaper option to add a load cell although it would be a bit more work and would require a Dremel tool with a grinding bit.

Half Bridge Load Cells are very cheap. You can get a 50KG one for $10.


https://www.sparkfun.com/products/1..._oNjFmCcUCvm1JUDzb-HbRsYnCCG5ZqLnMaAnhU8P8HAQ

All the ones I have found are too large to fit in the Pedal Spring Cartridge like the Button Load Cell will. For reference, the button load cell has a diameter of 25 MM.

IF, you were able to find one with its length 25 MM or less, you could create Two 25 MM (appx) shims out of wood. You would place one beneath the load cell and one above. This would ensure it sits level and flush in the cartridge and that the spring applies even and level force to it.

However, I have not found one that small. So the other option is to remove the brake pedal pad. Then take the load cell and trace out its pattern with a sharp edge into the large plastic piece the pedal mounts to ensuring the brake pedal mount screws will still screw in without hitting the load cell. After that you will need to grind out 1 MM or 2 so that you can set the load cell into the plastic base.

You will need to find some longer brake pedal pad mount screws. Use those to mount the pedal on top of the load cell. You will need to tighten it fairly strongly to prevent the pedal pad from leaning left or right while braking, as there are only 2 pedal mount screws and they are inline with the center of the brake pedal shaft. But you also can't tighten it too much or else you will have used up too much of the load cells pressure range.

End edit
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Thanks for the info.

I've been considering load cell as I drive h pattern cars a lot. Having a consistent pedal height would seem to make keeping consistent brake pressure while H&T downshifting easier. With the pedal moving its really difficult so I tend to ease of on the brake as I throttle blip.

The Ricmotec with the real pedal upgrade sounds like the best option but as you say it is expensive.

 

I have a Apelectrix load cell on my G25 pedals and am extremely happy with it. well worth the price if you can get one.

 

Thanks for sharing, although as you say, "if you can get one." How much pedal travel do you have compared to the stock pedal? 50%, 25%?

 

Nice find.
I've been using Ricmotech for about a year, can't complain of anything. Assembly is a bid involving but the pedal feels great. There is some initial break in period when it felt with almost no travel but after a week is't all good, travel is still limited comparing to stock spring, but this is expected for any load celled application. I think it's under an inch, but after adjustment to gauge brake strength by pressure instead of travel, works wonder, also heel-toe is a breathe due to pedals staying at the same level.
Highly recommend.

 

When I bought mine, I had to wait 8 mos or so for it. The pedal's movement is minimal, much less than 25% of the original movement. I press hard when I first get in the car to calibrate the pedal. The harder you press the more baking you get although the pedal doesn't move. I find it very easy to modulate the amount of force I apply and hence the amount of braking I get. I've been using it for 4 years with thousands of hours of use. Well worth the cost and wait to get it.

 

Good deal. Glad to hear it has worked good for you.

Yowzer. 8 Months... Much less than 25%, I don't think I would like that. Bare in mind I have read on the forum someone quoting a race car driver, or engineer that ideally, in a perfect world, the brake pedal is as firm as a brick. That would give the absolute best performance. I think that would feel quite unnatural to me though.

I would recommend you download DXTweak2. You should be able to set a maximum value for the brake pedal. So even if its capable of going up to 100KG for example, you press it as hard as you can to get your max value. Then use the tool to bring the max value down to what you want the max to be and save. From then on it will never go over that. You will still have to press the pedal down to that value in AC to "calibrate" in AC, but there will never be any variation from one day to the next.

 

I have the Apelectrix that I don't use anymore. I have spent no more than two hours, didn't like it because I prefer to have a bit of brake travel.
The Apelectrix barely moves at all, I even cut down one of the two rubber stoppers that came with it, still not enough for my preference.
I should sell it, it just sit in my drawer. Currently I am using the Fanatec CSP V2, which you can adjust the brake pedal travel.

 

I love the ricmotech load cell actually ... just need to swap the throttle spring with the clutch one ... otherwise, you can forget about heel and toe! the brake pedal is extremly stiff!