Fingers crossed it'll cut ally

The 7700kv motor is only for use in my model car!

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Originally Posted by blackburn mark

i didnt realise it was mentiond in this thread :whistling:

also irving came up with ideas but again its all a bit rocket science to me at the moment

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Yes modifying the servo tester is a good way of doing it. The problem is we'd need no know what the pot is connected to first..i.e the circuit diagram of the servo tester. I don't have any servo testers so I can't really help there yet.

The servo tester could be as simple as the one here:
http://pcbheaven.com/wikipages/How_RC_Servos_Works/
(There's some good info there on how servo signals work. It's the same for the ESC so worth reading.)
In which case you can't easily change the pot.
Maybe open up your servo tester and take a picture...

Going back to the connecting the parallel port directly to the ESC idea, I must just be explaining it badly.

Have you got a multimeter/voltmeter?
If so connect it between the pin you want the spindle on and ground on the parallel port. Set the spindle to full speed in Mach3 and check that the voltage is around 5v (definitely no more than say 5.5v).

If that's the case then for testing purposes just get two bits of wire, connect one wire from the ground (black/brown) wire on the ESC 3 pin connector to ground on the parallel port (any pin from 18 to 25). Connect the other wire from the output pin on the parallel port to the signal wire on the 3 pin connector (white/yellow/orange). DON'T connect anything to the red wire on the 3 pin connector.

From there just try the settings I mentioned earlier in mach3 and see what happens. I'm sure it'll become clearer once you've got it connected.


Do you use anything like windows messenger/Skype etc? If so that could be an easier way for me to explain this.

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Maybe open up your servo tester and take a picture...

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Attachment 3353Attachment 3352Attachment 3351Attachment 3350

dont know if you will make any sense out of these... its just a magic box to me :eek:

i do have a mulimeter but the pc with mach on it is in bits ready to go in my base but i will take you up on the offer of help when i get to that point in the build, iv only had a quick play with mach up to now.

iv just orderd a "MICRO MAESTRO 6-CH USB SERVO CONTROLLER ASSEMBLED" £12 ebay
im not sure if it will solve our mach spindle problem but i thought id give it a punt
Attachment 3356Attachment 3354Attachment 3355
im hoping mach will know what to do with it :question:

micro maestro 6-ch usb servo controller

Attachment 3357

I don't think mach3 will interface with the thing you've bought, not without a lot of effort. I might be wrong though. You could just run it in the background and adjust it manually on the computer anyway?

Servo tester, still trying to trace the PCB. I think it'll work with the parallel port...

Ok disregard that, just had another look. It should be simple to get the servo tester connected.

:idea: Here's a step by step guide.

1. Remove the potentiometer, or just desolder the pin connected to R32.
2. Solder a wire to the pin of R32 that was connected to the potentiometer.
3. Connect the other end of that wire to the chosen output pin on the parallel port...say pin 14.
4. Solder a wire to the negative of the circuit board, e.g. pin labled '-' on connector JIN, and connect it to any ground pin on the parallel port.
5. Set PWM frequency in mach3 to something high, like 1000.
6. Under Config-->Spindle Pulleys set max speed to the max RPM of your motor.
7. Cross fingers...it should work as normal with the rpm show in mach3 corresponding correctly.

Hmm, before you do that measure the voltage between the pin of R32 that's not connected to the pot and ground whilst twiddling the potentiometer and see what the range is...


Ooh, is that a programming connector I spy on the PCB! Could be handy for something.

Disregard steps 1 and 2, that's not safe to do if the parallel port outputs over 5v. Measure the max voltage as I said in the previous post then just desolder the switch and solder the signal output wire from the parallel port to the PCB pin of the switch which was connected to R31. Then adjust the pot untill it gives the same reading for voltage with mach3 at 100% spindle speed as it did with the pot at 100%. Good idea to remove R32 whilst you adjust the voltage, then put it back when you're sure it's right - that guarantees not to break anything. Quite tricky soldering though!

hahaha!! yove been busy jonathan... hope you werent late up this morning

iv still got loads of drilling to do so i cant afford to pull my servo tester apart at the mo but iv orderd one exsactly the same for you to experiment with (if you agree) , PM me your address and ill send it over to you once it turns up here.

if you manage to solve the issue then let me know how you did it and we'll call it even :smile:

ps: dont worry about it if its more than you can be botherd with :)

just for a refrence iv mesured the voltage between both sides of R32 with the resistor still in place

0.24v both sides 0 speed
3v both sides flat out

thats with 5.57v coming in from the ESC battery eliminator

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Originally Posted by blackburn mark

iv orderd one exsactly the same for you to experiment with (if you agree) , PM me your address and ill send it over to you once it turns up here.

if you manage to solve the issue then let me know how you did it and we'll call it even :smile:

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That sounds like a good plan :) I've sent the PM. I'll work it all out properly and take some photos of what I do when I get it.

If that voltage is 3v max then we can use the existing potentiometer to scale the voltage from your parallel port to be the same.