On/Off Interval & Speed Controller

[goodrobot]

Hi All,

I'm new to the forum and a complete noob when it comes to electronics, but I want to prototype an idea I have. To make my idea work, I need to be able to control the time the motor is on and the time the motor is off in fractions of a second - a kind of pulsing cycle - as well as the speed of the motor. I would also like to be able to control all 3 of these variables 'on the fly' with dials. Is there a controller that exists that will allow me to do this or would I need to build one? If I do need to build one, does anyone have any advice on how I would go about it?

P.S. The circuit will be 12v DC and the motor will be brushless if it makes any difference?

TIA!

GR

 

[Bluejets]

Pulsing the motor on-off in fractions of a second IS speed control.
Best done with a standard off-the-shelf r/c speed control available for maybe $15 depending on where you are and motor size.
This in turn can be controlled via a $3 servo tester from Ebay.
You will never build it for what you can buy it for these days.

 

[goodrobot]

Hi Bluejets,

Thanks for the reply! I appreciate that speed control is pulsing to a degree but I want to be able to control the speed of the motor independently of on/off intervals which should be variable from say... 0.5 of a second up to about 3 or 4 seconds which also need to be controlled independently (on time and off time). Is there such a thing?

Thanks.

GR.

 

[Bluejets]

I hesitate to ask why however you could use any timer module, again off Ebay for a few dollars, to switch the input to the aforementioned speed controller.
There would be some serious inrush currents to consider which may make toast of the controller as it was never designed for such " rough" treatment.
Besides that, they are usually designed to be armed on each successive power-up.
Any input timer would also be preferrable to use solid state switching as opposed to relays.
It might be more advantageous to simply explain what you are trying to achieve as I'm almost certain there would be alternatives.

 

[goodrobot]

I'm trying to create a fully adjustable imitation breathing rig for a series of props I'll be making next year. The props will be animals and I'd like to simulate various breathing states. E.g - in one scene the animal may be taking short sharp breaths and in another longer slower breaths or even longer faster breaths. The motor/pump will only need to work in one direction as the 'balloon' will take care of the exhale during the 'off'. The 'balloon' already has an electronically controlled valve which I have no interest in tying into the rest of the rig. I don't want any of the variables (Time on/Time off/speed) to be tied to each other in any way. Again, I would like to be able to control all 3 variables using dials on the fly.

Any ideas?

GR.

 

[duke37]

Swiching a motor off will not stop it instantly due to the inertia. If you wish to rapidly stop the motor, then a stepper motor would be preferred.

 

[goodrobot]

Hi duke,

Thanks for the advice. Should that also facilitate the rest of what I'm looking to do? Timing on/off/speed independently?

GR.

 

[duke37]

The simplest cicuit I can think of is shown. It uses a 4093 CMOS quad schmitt NAND gate.

A stepper motor and controller is outside my knowledge but you could program it to do whatever you want.
The speed may need some modification.

 

[Bluejets]

If say a permanent magnet motor ( for example a battery drill motor) is tied to a compressor then it will stop fairly quickly, granted not instantly but perhaps acceptable.
Use of that would simplify requirements.
So as I see it, 2 timers, one for on-off seriesed up with another for speed control via variable astable.