PWM DC motor controller

[BlackSportD]

I bought and built this PWM DC motor controller kit
CK1400 DC speed controller

As of now taking readings from RV1 10K at 100% duty cycle it is about 12vdc. I'm hoping to remove that component and modify whatever else so that I can have an external 0-5vdc control 0-100% duty cycle, or at least 0-80%.

If not does anyone know of a kit ready to go for this or modifiable to do so?

 

[colin55]

Q1 is an emitter follower. If you turn it into a common base stage, you will be able to control the base with 0-5v or less (0-2v).

 

[BlackSportD]

Thanks for the advice. I'm not familiar with transistor setup verities, but from looking into what you said I should remove/jumper R2 (or keep it for Emitter degeneration), move the connection point from the emitter to the collector and put a resistor of appropriate value ahead of the new connection point?

Should I then remove C1 and R7 along with the pot RV1, P1 and R1? Should I put a current limiting resister inline with the 0-5volt control source?

Should I take a reading at NE556 pin3 to see what my range is there?

 

[colin55]

What is the impedance of your 0-5v input voltage.

In other words, does it come from a source that can deliver 0.005mA or more than 100mA

 

[BlackSportD]

I'm not sure, but I would guess it can put out more than 0.005mA, probably more than 100mA too.

 

[colin55]

When you incresae the voltage on the pot in the cirucit above, does the motor increase or decrease in RPM.

Is this what you want or do you want it in reverse?

 

[BlackSportD]

When I increase the voltage out of the pot, the motor increases in speed. I am wanting to control the 0-100%PWM with a 0-5volt dc control (0-12volt comes out of the pot), if a reverse of that function happens from the modification, I can live with that.

 

[colin55]

Measure the minimum voltage at pin 5 at the point (when the lowest speed acceptable), is attained.
Measure the voltage at pin 5 at the point when the highest speed is obtained.

 

[BlackSportD]

Will do, I can do that Wednesday.

 

[BlackSportD]

I found this kit that looks very simular
PWM motor controller

And it looks like they make an alteration board to give it the functionality I'm looking for
0-5volt control kit

I've seen this board before, but this site makes that extra circuit for it that I haven't seen until now. It looks very simular to mine, but it seems to use four transistors.

 

[Boncuk]

When you incresae the voltage on the pot in the cirucit above, does the motor increase or decrease in RPM.

Is this what you want or do you want it in reverse?

Motor rpm increases by increasing the base voltage, thus increasing the control voltage of the timer IC.

100% rpm can be obtained by shorting or omitting R1 (560Ω) and turning both pots to maximum output voltage.

At +UB=12V the control voltage will be as high as 11.1858V. With R1 it will reach 10.6247V, which means a drop of 561mV of control voltage.

To reverse the motor it must be connected reverse.

Boncuk

 

[BlackSportD]

Boncuk, do you see a way to alter my current circuit to work off of an external 0-5vdc control? I'm about to buy the other product but would like to avoid having to do so.

 

[Boncuk]

Hi BlackSportD,

the pulse length of the circuit depends very much on the control voltage supplied for the timer circuit (IC1A) in relation to its supply voltage.

When changing to an input voltage of 0 to +5V you should adapt the timer's supply voltage to be the same (+5V). Connect the motor to the desired supply voltage. (The relation will be the same as before with a lower voltage.)

In short words: Connect the entire control circuit to a supply voltage of +5V and the motor to any voltage not exceeding the IRF530 rating. Use the +5V power source to control rpm.

Omit R1 since it won't allow 100% rpm.

For a good starting rpm adapt R7 (now 2K2). If rpm is too low increase that value. Adjust for max rpm by rotating RV1 (10KΩ) to the max clockwise position and do the rest by adjusting P1 (500Ω).

Switch off the power and rotate RV1 to the minimum position. Restart the circuit and check minimum rpm. This is dependent on max rpm setting. If necessary adapt R7 value.

When done, don't change the setting of P1 anymore.

If you purchased the kit just connect +5V to V+, and the motor supply voltage to E+. Connect both ground connections to V- respectively E-.

Don't short LK1!

The motor will be connected to M+ and M-.

Boncuk

 

[BlackSportD]

^^ Simply awesome. I had hoped it would be somewhat easy. I had emailed the creator of the kit and I could swear it seemed like he knew less than I, I seriously doubt he was he he said he was.

I did purchase the kit and have already assembled it. I will disconnect LK1 first so that I do not forget haha.

The kit advertised that as-is, it allows 0-100%RPM, supposedly P1 is there because the voltage, even after R1 could get to the point of having the control circuit "skip" over itself, surpass 100% output and go back to very limited output. But I will take your advise on R1 and R7, especially with that part of the circuit now using only 0-5vdc range, thanks for their calibration advise.

Very exciting.

I'm worried about electrical noise though. I was looking over other google'd 0-5vdc controlled controllers (much more expensive industrial stuff) and I found it mentioned more than once that if 0-5vdc was used for control, an additional filter circuit had to be purchased. Do you think this kit is "noisy".

Thanks big time! I'm going to try to test this out today now that I'm home.

 

[Boncuk]

Hi BlackSport,

may be the circuit will go somewhere beyond 100% (where 100% is steady on). Simulation shows it will be 100% if R1 is omitted or shorted. I suggest to use a jumper to short R1 or leave it connected.

I guess this circuit will produce a lot of noise, not only electric noise, but also audible noise from the motor by a whining sound.

I made a similar circuit for a brushless fan rated 500mA and the noise was very annoying. Instead of using 100nF for C7 you might try different value electrolytic caps starting at 10µF.

It is said that the cap nulls (or minimizes) PWM, but my experiments prove that the noise was reduced to almost zero with a much better starting behaviour of the motor.

Regards

Boncuk

 

[BlackSportD]

R1 will have to take a hike as my test motor is not getting anywhere near 100% with both pots to the least resistance.

Another dissapointment w/ the kit is that at 0/full off the pump is still making a lot of noise, typical of a motor single-phasing. I hope with the new slew of mods that that will go away.

To provide a constant 5volts to the control circuit, could I use a resistor from 12vdc, or would I need to make another circuit all-together with a voltage regulator?

 

[Boncuk]

You might change the value of R7 for a lower one. Try 1KΩ and see what happens.

If the motor is still noisy the power MosFet also conducts at minimum setting which won't allow the motor to start and produce noise instead.

I wouldn't recommend PWM to shut off the motor and use an additional switch for motor supply voltage instead.

Starting the motor at very low power settings it might burn up without rotating.

For a constant +5V power source you can use an LM78L05, a low current (100mA) regulator. Connect it to the motor power source and use extra smoothing caps around it.

Boncuk

 

[Junker_eu]

I think you imagine the issue more difficult than itself.Maybe,you just need to do like this : short the R1,then supply the Controler circuit with your supply of DC +5V.Look into the effect at first.

 

[BlackSportD]

This is a mess haha. Maybe an RC ESC is in order. Those are very affordable and capable, just need to find on that is single direction and a way to convert the input to 0-5volt.

 

[BlackSportD]

I think you imagine the issue more difficult than itself.Maybe,you just need to do like this : short the R1,then supply the Controler circuit with your supply of DC +5V.Look into the effect at first.

I want to do that, and to do it quickly I'm wondering what resistor to go with to test this (step down from 12v to 5v) to avoid buying more components (voltage regulator). It would seem that any voltage to the control circuit at all causes the hum and single phasing sound from the motor, and a relay will have to put in place to have a true "off" at minimal settings.

But now the ESCs are looking good, but its been hard to get detailed info on the internet about them.