What's the difference controlling a 180v PMDC motor to controlling a 12v PMDC motor?

bigal_scorpio said:

Hi Mate, I have played with the trimpots and got the softstart a bit quicker but even then there is the 3 second run up and run down times that I can't change.

As for the speed control, maybe I didn't realise I didn't mention that there is no pot but only buttons to change the speed or select 3, 6, 9 or 12 kph so I cant really use them for a lathe. Something else I forgot is that I would also like an emergency stop that braked the motor if possible? You never know if something is going to get caught or even start a massive wobble with an uneven blank!

Al

Click to expand...

I think we can work on those requirements, like me look into it.

how about this?
https://www.circuitstoday.com/dc-motor-controller
Use your igbt &diode and make your own PWM

Ok I am assuming this is 220 volt AC line power?
Where does the wire go that is glued to the board?
The pots may also be MIN and MAX speed.
The control panel may be ramping the speed thru the speed control input to the board which may be that wire that is glued to the board.

kinarfi said:

how about this?
https://www.circuitstoday.com/dc-motor-controller
Use your igbt &diode and make your own PWM

Click to expand...

He would sill need to make the power supplies for that.

Is the motor brushed or brushless? Some BLDCs won't like being PWM'ed.

4pyros said:

Ok I am assuming this is 220 volt AC line power?
Where does the wire go that is glued to the board?
The pots may also be MIN and MAX speed.
The control panel may be ramping the speed thru the speed control input to the board which may be that wire that is glued to the board.

Click to expand...

Hi mate, the pots don't seem to affect the ramp at all but one of them causes the motor to stutter at full scale so I think you are right about them being min and max.

The wire that is glued is actualy six core going to the display and buttons. I have not been in the display part but I will do and report back. There may be more electronics in there than is needed for the serial LED displays etc. I will check.

And yes this is 220v ac here in the UK it is nationwide.

Al

kinarfi said:

how about this?
https://www.circuitstoday.com/dc-motor-controller
Use your igbt &diode and make your own PWM

Click to expand...

Hi mate, I still don't know how much if any of the original I can cannibalise usefully. Hopefully I can retain the parts of the circuit that power the mill and if so I could maybe do something on these lines.

Thanks, Al

alec_t said:

Is the motor brushed or brushless? Some BLDCs won't like being PWM'ed.

Click to expand...

Hi Alec,

I don't know if it is brushless? Can you tell without opening it? The pictures show a bulge at each side roughly where brushes would be if it had them.

Whats the best way to check?

Al

bigal_scorpio said:

Whats the best way to check?

Click to expand...

I'd try an Ohmmeter across the terminals. I would expect a brushed motor to show a resistance varying somewhat (say by no more than ~50%) with shaft position as the brushes switch between commutator segments, whereas a brushless motor would read open circuit at all shaft positions because internal semicon switches are in the off state.

Now I have the motor our I can see it has brushes! Was hard to see in its space. Also I have found more electronics, another 2 boards from the display! One just has switches and a nine pin sil connector to the display board. The main display board is much more interesting though.

It has 2 x 2 pin pulse connectors, 1 x 2 pin safe connector for the safety pull tag and the 9 pin connector to the switch board. Besides those there is a 5 pin connector that goes to the motor board and is marked Send, Rev, Vcc, Gnd and Saf. Another connector with all the same markings except Saf and 2 separate UNUSED connectors marked Speed and Inc/Start, they are both 3 pin.

This board also has a 12Mhz processor and a couple of 7 seg ICs, also there is a small daughter board on legs with one of those black blobs on it like the kind on boards from childrens toys etc. The processor I mentioned is a MegaWin MPC 89E52AE which according to google is an 8 bit 8051 series Microcontroller.

This board seems way too complex just to be a pulse monitor and LED segment driver so I wondered if it contributes to the actual running of the machine and further wonder if the board was made with multiple models in mind? This leads me onto my final thought. Does the board accept input from the switches EITHER/OR the other two 3 pin connectors which, hope beyond hope I thought may be for a more basic model with just a couple of pots to set the speed and other details?

I will get some pics and hope someone knows more about it.

Edit: here are the pics.

Al

I just had a thought. If the speed connector was designed for a pot then two of the pins should be Gnd and steady +v?

If this is true then is it worth trying a 10k pot on it?

Al

You might be better off just salvaging the power components, then building a little PWM circuit to drive them.
My bet is once you start disconnecting stuff from the boards they won't perform.

ronv said:

You might be better off just salvaging the power components, then building a little PWM circuit to drive them.
My bet is once you start disconnecting stuff from the boards they won't perform.

Click to expand...

Hi Ron, Yes that was my first thought but since seeing the complexity of the contol board I am now wondering if the motor board is purely a slave and only controls the motor by getting signals from the board with the 8051 on board.

Trying to think of a way to test the theory, any ideas?

Al

there is a 5 pin connector that goes to the motor board and is marked Send, Rev, Vcc, Gnd and Saf

Click to expand...

This seems some sort of serial communications plus a safety line.
Does the motor do anything with the 5 pin connector disconnected.
At this point I am going to say its not an off the shelf motor controler but we still may be able to get it to work.
Can you try to hook up a pot to the spot where a connector would be labeled "speed" on the motor controler?
The pot should be around 10k to 100k ohms.

Hello All,
I think this might suit your needs and is relatively reasonable priced. https://www.surpluscenter.com/Elect...rs/90-180-VDC-SPEED-CONTROL-W-POT-11-2269.axd I don't know if they ship outside the USA but might be worth checking into.

ronv said:

You might be better off just salvaging the power components, then building a little PWM circuit to drive them.

Click to expand...

I agree with Ron. Now that we know it's a brushed motor a PWM drive should be ok.

I can see where you are tempted. Almost everything you need is on the little red board.
Top right is a little switch mode power supply - probably for the low voltage circuits. It uses the TNY278.
Bottom right input power and maybe a relay to enable the high voltage.
Across the bottom the high power bridge, IGBT and clamp diode.
But then the top left that looks like a small micro. Therein lies the challenge.
But tour right there is not a lot of "stuff" coming into the board.
Where does the black cable go?
Is that a connector below the word speed?

ronv said:

I can see where you are tempted. Almost everything you need is on the little red board.
Top right is a little switch mode power supply - probably for the low voltage circuits. It uses the TNY278.
Bottom right input power and maybe a relay to enable the high voltage.
Across the bottom the high power bridge, IGBT and clamp diode.
But then the top left that looks like a small micro. Therein lies the challenge.
But tour right there is not a lot of "stuff" coming into the board.
Where does the black cable go?
Is that a connector below the word speed?

Click to expand...

Black cable 5 conductor goes to the display controller board. May be serial communication.
I think the spot labeled speed is where a connector would go for a speed pot.

4,
If you could find the driver ic a 1 chip pwm and an opto isolator would probably do it.
Maybe part numbers of the ICs at the bottom left??

Here are some updated pics with all IC markings I could find.

Are they any help?

Al

EDIT: 6 pin should read 5 pin, I blame these warped old fingers!