[taiwanluthiers]

My G0704 had some issue with the motor basically spinning really fast and then slowing down or stopping suddenly, kinda like revving a motorcycle engine. I discovered that there are pots on the control board, and played around with it (with the thing running) until the motor ran smoothly. It seems the IR pot does most of that.

Are there any explanation of what those pots do? there's one labeled C, a IR pot, a min and max pot. There is also another pot that has no label (and moving it does nothing it seems).

I know people here mess with it to get higher RPM than available but what about going the other way, like I want to limit max RPM to about 1000, but with good low end torque for machining steel.

[john-100]

you may find what your looking for here-

Variable speed controls - The Warco

Attachment 337606



John

[109jb]

A couple tidbits that may help

https://www.youtube.com/watch?v=SfrEuHpZwv8

and page 45 here

https://www.damencnc.com/includes/do...d-e2c0ef10ae8e

[john-100]

looking at the speed control circuit diagram

Attachment 337678

you have across a 12V DC supply
the speed control potentiometer and the minimum & maximum presets in series
so if the presets are set to minimum resistance you have the maximum range of speed control

no volts = zero speed and 12V = maximum possible speed as you would expect
the min & max presets do exactly what you expect

if you switch on with the speed at maximum or turn it up very rapidly , you will find the 100K acceleration preset R4 in conjunction with the 22uF capacitor (C101) adjusts the rate the motor can accelerate

minimum resistance = very fast acceleration and from standstill will result in a very large starting current
acceleration preset at maximum (100K) = slow acceleration

the diode across the acceleration preset results in the motor immediately following the speed control as its turned down

the voltdrop across the "horse power "resistor R21 is used to measure the motor current and is used by 2 circuits

first is a comparitor that compares it with the adjustable voltage from the current limit preset
when the limit is acceded , the comparitor short circuits the speed demand voltage comming out of R10 , before it goes into the 2nd op-amp

second circuit is the IR compensation circuit
this time the voltage from the horsepower resistor is amplified by an op-amp with some frequency selection network
the resulting voltage is adjusted by R29 the IR preset and is used to give an amount of positive feedback to compensate for the IR losses in the armature windings

if its turned up too far the motor will runaway !!


John

[taiwanluthiers]

I had to play with it a bit.. I want the min speed to be about 150 rpm but that's really hard, because the motor will sometimes not start at all in that state.

The IR thing if I keep it too low, the motor will run smoothly but as soon as I do any cutting at all the motor will stall!!! If it's too large the motor just keeps revving up and down.

I ended up having the minimum RPM about 3-400 (this will be too fast for drilling anything) and a max rpm of about 2000. Keep in mind this is at the low end of the belt drive kit so meaning the motor itself is actually spinning at 600rpm at least.

This motor just seems to lack any torque whatsoever... it's almost like the drive train itself is enough to slow it down a lot. Maybe I should just get a single phase 1750 rpm motor and not have to mess around with controllers.