Comments for Airtripper's 3D Printer and Arduino Blog 3D Printer usage and modifications plus Arduino powered electronic projects and 3D Printing designs. Thu, 16 Oct 2014 23:43:36 +0000 hourly 1 Comment on Arduino Load Cell Circuit & Sketch for Calibration Test by Mark Heywood Thu, 16 Oct 2014 23:43:36 +0000 The load cells I’ve tested have been around 1000 ohms. 350 ohms will allow more current to pass so you will need to look at the INA125 datasheet to check the current level is within tolerance.
To get readings from the load cell in both directions you will also need to add a negative supply. The datasheet has little information about dual supply set-up. The above circuit has 12v supply so a -12v would also be required for a dual supply set-up to read the full negative range of a load cell.
Implementing a dual supply with this chip is something I’ve not attempted yet.
While load cells can be read in both directions, some load cells can have a read dead spot/area where there is no preload. This is something to consider when attempting to calibrate a load cell without a load.

Comment on Arduino Load Cell Circuit & Sketch for Calibration Test by John McGeorge Wed, 15 Oct 2014 19:57:12 +0000 Hello,could I use this circuit for a 350 ohm 1.991 Mv load cell for my shock testing tool.The only problem is it needs to work in both directions to measure load of shock in compression and rebound(extended).Thanks in advance for any advice or help.

Comment on Arduino Load Cell Circuit & Sketch for Calibration Test by Mark Heywood Fri, 25 Jul 2014 21:55:40 +0000 Hello,

To increase the analogue gain you need to reduce the resistance of the trimmer pot. You would only need a 200 Ohm trimmer pot if the gain is too high with the 100 Ohm trimmer pot.

To clarify, to get the gain you need, if you are using a 5kg load cell, a 5kg load needs to be put on the load cell. If you are not reaching the the target gain, try adding extra weight to the load cell to see if the gain rises. If the gain rises, it might be that the load cell is under rated; you have 7.5kg rated load cell being labelled as a 5kg load cell. This can happen if there is going to be an initial weight being added to the final application such as a weighing platform.

If the gain stops below the target analogue reading, even after adding more weight to the load cell, I would suggest building the breadboard circuit shown above and retest the load cell and test other load cells if possible until you are satisfied that the circuit is functioning properly, and then go back to your PCB circuits for review.

I’ve tested five load cells with the same breadboard circuit above and not had the issues your experiencing so it’s just a case of replicating what I have done above and work from there.

Send me an update through the contact form and we’ll try and get your project sorted by regular email.


Comment on Arduino Load Cell Circuit & Sketch for Calibration Test by heggermont brecht Fri, 25 Jul 2014 16:50:51 +0000 hello

I have a little problem with the calibration of my load cells. I made a PCB with 3 the same load cell circuits on the sa as you used above. I tried different trim pots to calibrate the circuit. First a 100 ohm then a 200 ohm but I always get a maximum analogue value of around 866. Is it possible that I need a greater value of restistance or is there something wrong with my connections?

Comment on Airtripper Extruder Filament Force Sensor – Design & 3D Print by Mark Heywood Sun, 20 Jul 2014 01:50:37 +0000 Hello,

Thanks for the kind comment about the blog, I only wish I had more time to knock out more regular posts.

Well, about the patent claimed by Makerbot, it seems like they have patented an idea rather than a piece of technology. So while they are claiming to own the market for 3d printers with force detection, I could claim that 3d printers with force measuring is open source; based on what I’ve published.

The difference between the patent claimed and my idea is that the patent claim is about force detection, while my idea is about force measuring. I think there is enough difference between the two methods not to conflict and cause legal issues. The patent makes no claim about measuring force feedback from extruding filament, it seems like impact detection or object proximity detection at the tool head tip position is about the limit of the patent claim, and I reckon it’s about owning the market for self leveling build platform printers.

In any case, the patent purpose is to attempt to stop other 3d printer sellers and manufacturers from selling printers with force detection. However, the patent is unlikely to stop 3d printer owners from adding their own force detection tech.

Josef Prusa’s implementation of the force sensor predates the patent application but the idea is not close enough to effect the patent; since it only measures filament force and not tool head impact against another object.


Comment on Airtripper Extruder Filament Force Sensor – Design & 3D Print by Pome Adam Fri, 18 Jul 2014 21:26:32 +0000 Hi,

I found your article very interesting when it came out. But now I read that makerbot has patented a force sensor on the extruder to detect malfunctions.

I wonder how you feel about it? And I wonder if your publication could invalidate their patent?

By the way, your blog is awesome.

Comment on Marlin Firmware Home Offset Guide Using G-code M206 by The_ccm Sun, 08 Jun 2014 11:30:05 +0000 Ok thank you. It’s weird because I can’t save offset with M206, when I type m206 Zxx.x then M500 and M501 line 206 is not printing on the serial. Others settings are stored fine and can be changed.

Comment on Marlin Firmware Home Offset Guide Using G-code M206 by Mark Heywood Sun, 01 Jun 2014 19:41:54 +0000 Hello,

The gap distance between the nozzle zero position and the bed will be mostly influenced by how well the filament sticks to the bed. With my latest filament, it needs to be pushed right into the bed to prevent warping and lifting around the edges. I think as long as the first layer goes down ok, you are good to go, Getting the exact gap distance to match the nozzle is not vital, subsequent layers will be correct anyway.

Basically, all the settings listed with the M501 g-code command can be set the same way as the home offset.

The Mendel90 is a nice printer, a good design, it should serve you well.


Comment on Marlin Firmware Home Offset Guide Using G-code M206 by the_ccm Sun, 01 Jun 2014 17:35:09 +0000 This is a very useful and simple guide, thank you ! I finished my Mendel90 1 week ago and was always updating configuration.h for Z_AXIS_HOME after measuring so it was very boring. One thing I am missing if my nozzle size is let’s say 0.35mm zero, we should have 0.35mm between nozzle zero position and the bed ?

Also can we also store the E_STEPS_PER_MM value, for example M92 Ennn.nn then M500 ?

Comment on Marlin Firmware v1, Basic Configuration Set-up Guide by Mark Heywood Fri, 25 Apr 2014 23:37:37 +0000 Hello,

You will need to explain how far you have got with the firmware configuration, and have you connected to the firmware from the PC with software such as Pronterface or Cura. The firmware may not allow the stepper motors to run if there is no hot end temperature sensor connected. Also, the stepper motors will not operate properly if the end stops are not configured correctly.

It might take a few posts to get you sorted and it might be better to post your question on 3D Printing google group for faster response; link below.


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