Makita RT0701C - G-code control of spindle speed project

What resistance potentiometer are you using?
Depending on what it is, it may be easier to replace the servo with a digitial potentiometer.
Or it may not even be needed. The Makita may be using the potentiometer to adjust a voltage reference which tells the router how fast to go. Emulate that directly and get rid of the potentiometer completely. Use simple analog circuitry to convert a PWM into a flat voltage.
Any ideas on how the speed is controlled on the Makita?

Tried the digital. That was my first choice, but that didn’t work (even Microchip guys couldn’t figure it out).

Any connection to the control wires caused the router to run full speed.

So, I just isolated the pot.

I maybe way off target but there is a guy called AVE on youtube and he does tear downs of different machines, i think he says they used a Hall sensor switch, I will try and find it.

I finally got some more time to work on this project and since I was messing around in the electronics I decided to go ahead and build a controller for my next machine. I still have some clean up work to do on the Makita and some software tweaking to finish. I went ahead and added the tachometer to the system.

Now all I need is that robust machine I’m hoping Inventables is working on. :smile:

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Here’s the wrap-up for this thread.

All of the hardware is working as expected including the added tachometer function.

Now I have a little software clean-up to do and then I can put this controller to work. It’s a little overkill for what I have now, but it is very expandable for the next machine that I build.

Spec’s

Master A/C switch (all non USB power)
One master switch A/C outlet
Two G-code controlled ganged A/C outlets (one SSR controls both, could be split if needed)
600 watt 24 volt power supply
Reset/Feed Hold/Cycle start switches
Probe/XYZ Homing switch inputs
Router speed control output
Tachometer
4 axis (two can be used as Y1/Y2) 4.5 amp stepper motor controllers
Main controller is the Arduino running grbl version 0.9j (and sometimes testing with 1.0c)

I’ve had a lot of fun putting this together.

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It took me about 4 different circuit designs to get it working. I destroyed my router the day I got it as I had no idea what was inside the potted control box. After a autopsy I found out that there was no microcontroller inside. There was a Telefunken U211B3 chip instead, which is designed in 1996 by the way. I think I killed the chip as I tried to connect it straight to my Arduino which was powered by an earthed USB. I got a new control box from Ebay and for some reason its voltage was 5.2V and my first one’s was 3.6V. Maybe it has completely different chip inside it.

Next I tried my circuit with an opto-isolator. The problem was that the control box could supply next to no current at all. 0.5mA of current collapsed the controllers voltage and limited the RPM range I could get from it. The solution was to add a double insulated power supply and a linear regulator that I used to fine adjust the voltage. This way I did not have to worry about current consumption of the digital potentiometer and the isolator. Now I can even widen the RPM range on the router by making the voltage just a bit higher.

I attached a schematic below. I have only tested it on the bench as I have not yet built my CNC. I have no idea if the router has enough torque on the low RPMs.

I take no responsibility so use this circuit at your own risk and only if you understand what is going on with it. If you have questions I can try to answer them but I am not an expert on electronics.
Makita_speed_controller_MCP4161.pdf (66.8 KB)

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@ViljamiPirttimaa

Thanks, for posting your control hookup. I’ll check it out. It is a better solution than what I came up with, but I didn’t have any information on the internals of the Makita control circuit.

Do you remove the Makita speed controller, or parallel your device with the Makita controller?

I just removed the original potentiometer. You could add a switch to switch between the two though.
The leads with alligator clips are coming from the routers control box. The 9V power supply is coming to the back side of the breadboard.

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I would just remove the old potentiometer.

Thanks, again for the circuit.

Don’t know when I may get a chance to try it out.

Larry

Cool, I’ll post my experiences once I have built my CNC.

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@ViljamiPirttimaa

Just thought I would post my progress. I converted your schematic to my schematic program and did a board layout just for fun. Haven’t done anything with it yet. I’m not sure I can solder a SOIC.

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Looks good. I was scared of the SOIC soldering as well but actually it was very easy. At least with solder paste and a hot air station but I think it should be doable with a regular soldering iron as well. There is some good videos on Youtube to help.

I have been waiting for some parts so I haven’t completed my mill yet. Hopefully I’ll get it going soon.

I have soldered (low volume) SOIC components and it was aqtually quite easy to do even with a generic heat gun (Black&Decker) :slight_smile:

What you do need is solder paste.

Preheat your kitchen oven to 120degC (250degF), place your PCB with solder and SOIC inside for 5min to heat it up. If you do have a metal plate with some thickness to it you can place the PCB on that so it will maintain heat better once removed from the oven.
Once taken out, go over the PCB with the heat gun, start 6-8" awayat high heat/low air flow and gradually go closer untill the solder paste turn silver. Once it does that maintain heat for another 5-10sec to make sure all pads reach proper temperature.
Allow to cool and you should be done :slight_smile:

You can skip the oven altogether but the gradual increase/decrease of temperature is easier on the PCB. However this is more relevant for multilayer boards vs single/double sided PCB’s.

Following this topic. Please report back with any findings.

@ViljamiPirttimaa, @RobertMitchell

I finally got everything together and this design works for me. Thanks again for sharing your findings.

I ended up just using a soldering iron to solder in the SOIC package.

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Looks great! I finally built mine as well and it is working. My electronics enclosure is not any bigger than it needs to be so I had to put a few other things on the same board :slight_smile:

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@ViljamiPirttimaa Is that an xpro controller under the fan?

Yes. I designed that 3D printed fan mount to ride on top of the 10 pin and 6 pin connectors on the xPRO. It takes 5V from the 6 pin header. https://cad.onshape.com/documents/9c124d1502f4031b1e0a1865/w/1c0b8a66fcd19e05899220f6/e/897f7a3262bf63e7283b9811

New digital RPM control integrated with my CNC controller.

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@ViljamiPirttimaa, @LarryM

Thank you for your input to creating spindle speed controller. Finally I am going to modify my Makita as well.
I would like to to ask you, would you be so kind and share with me Arduino sketch, so that I have some starting point?

I would appreciate if you could share it with me.

Thank you.