PWM DC motor controller

[BlackSportD]

Interesting results. I cut the jumper (LK1) that feeds 12vdc to the control circuit.

Wired the 12vdc to E+/-, no hum.
Wired in a 9vdc battery to the control circuit V+/-, motor seems to run at 100%, no PWM.

RV1 has no effect, no control. I put a 1M ohm resistor in series w/ the 9v power supply, pump doesn't run at all, no noise. I put a 1K pot in series, 1ohm the pump is on, turn the nob into resistance and kaput.

Seems the control circuit does not like anything much under 9v.

 

[BlackSportD]

Maybe a totally different approach can be taken to keep things simple, what would be a good way to convert my 0-5volt to 0-12vdc? The middle pin of RV1 outputs a simular voltage to control the circuit. I could have RV1 completely deleted, how would that work?

 

[Boncuk]

Hi,

with a 1MΩ resistor in series with the power supply you won't get any result, but if you're using a battery this measure guarantees very long battery life.

Even if the resistor shorts that power supply the resulting current drawn is 9µA (0.000009A).

I'm getting convinced that there is a false connection somewhere in your wiring.

Please recheck - and if necessary rip off the entire circuit and and redo.

The circuit should run with e.g. 12V motor supply and 5V supply (and control) voltage for the timer IC.

Stepping up from 5 to 12V doesn't make much sense to me. An SLA battery is cheaper and has an absolutely clean DC output.

Boncuk

 

[BlackSportD]

My 0-5volt feed is coming from a "smart" source that I want to use to control the motor, thats why it almost seems worth it to have that 0-5vdc stepped up to be used at the center pin of RV1 as if it really were the output of RV1 and bang, done.

I will go over my wiring/board.

 

[colin55]

I looked at your circuit and it is going to be very difficult to convert "0v to 5v" from your control line to "0v to 12v" as required by the 555. The only two ways around this are:
1. Put the 555 on a 5v supply.
2. Use a completely different circuit such as an op-amp.

 

[Boncuk]

Hi BlackSportD,

please compare your wiring with the one attached here.

The circuit works 100% using the supply voltages as shown.

If you just want to use a 0 to 5V input voltage for control connect the input voltage to pin3 of P1. Omit R1 and JP2. You must connect the collector pin of T1 to a constant voltage of 5V in any case. (Don't neither connect it to the variable 0 to 5V input nor to the motor supply voltage.) The same applies to the supply voltage of the NE556.

The circuit was simulated with ISIS (PROTEUS) which shows it is working from zero to 100% rpm.

Boncuk

 

[BlackSportD]

I looked over everything again, and along side a picture of a completed unit and I can't find where anything is wrong. I even removed and re-inserted the 556.

It works when 12vdc is used in the control circuit, and with 9vdc the pump goes to truly 100%.

Along with the retesting that went with this, I noticed that if the circuit is placed on 12volt control, pot tuned all the way down (0%) to the point where the pump does not spin, just make it's single phasing noise, when taking that control voltage off the pump would jump.

*Edit-- after reviewing the online PDF, it says the operating range is 5-16vdc, and in the paper that actually came with the kit 9-18vdc. Looks like they did a revision, and found that anything 9vdc and below won't cut it for the control circuit and that would explain the odd operation w/ the 9volt battery and when using a resistor to lower that voltage even more.

I bought the other circuit that has the 0-5v control modification included to now mess with, this thing will just make me shoot something.

I might end up buying this also--
**broken link removed**

Boncuk, my up-most thanks for all of your effort.