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### Topic: converting astable multivibrator for DC motor (Read 4376 times)previous topic - next topic

#### Terraviper-5

##### Feb 03, 2013, 11:33 pm
Hi!

For my project, I need a swinging motor. I thought the only way I could do it is by buying motor shield R3 for my Arduino Uno R3, and instruct the mcu to cut power, reverse dir, give power, etc. Then I found out that there is a circuit that can get rid of a lot of complexity in my program and save me one pin on mcu, only the pin that gives/takes power remains. That circuit is the one from the title. Now, every search I make on Google brings up that circuit for LEDs, but when I search for it in combination with motor, it only brings up YouTube videos, not an actual diagram. As I am not very familiar with electronics, I am not sure as what to remove/add to the circuit, so that it can work with an electric motor. I also want to add a potentiometer, so that I can regulate the frequency of swinging. The motor would be a standard DC motor, 12V, 1A (at max load) from a printer.

One of images from Google for reference:

#### 0AlphaOmega

#1
##### Feb 03, 2013, 11:55 pmLast Edit: Feb 04, 2013, 12:02 am by 0AlphaOmega Reason: 1
Swinging?
Are you maintaining the swing of a pendulum?
If so don't forget that a pendulum will have a resonant frequency dependent upon it's length.

Replace the LED with an LED opto-coupler on either the Arduino or the circuit below.

How many wires does your printer motor have?
For whom does the clock pulse? It pulses for you!

#### Terraviper-5

#2
##### Feb 04, 2013, 02:26 pm

Swinging?
Are you maintaining the swing of a pendulum?
If so don't forget that a pendulum will have a resonant frequency dependent upon it's length.

Replace the LED with an LED opto-coupler on either the Arduino or the circuit below.

How many wires does your printer motor have?

Thanks for the warning. I am actually electrifying a bell

probably has its own resonant frequency, but ill be careful.

Motor has 2 wires (even though the connector has 3, only 2 are actually connected to the motor).

You mean add an optocoupler between the Arduino and transistor, that will control power to the multivibrator circuit? Yeah, that's probably a good idea. But how do I actually connect the motor? My problem is here:

And I will probably have to add kickback suppression diodes somewhere?

#### ash901226

#3
##### Feb 04, 2013, 06:35 pm
you need a H bridge that control by an opto couple then this could be use
btw the third leg is it connected to anything body or something

#### Retroplayer

#4
##### Feb 04, 2013, 07:12 pm
I'll preface this with the disclaimer that I hate when people suggest changing my design instead of answering directly, but in the case of a bell, have you considered a mechanical oscillation method? Then you only need to move the motor in a single direction. Very, very simple.

An oscillation could be provided by a cam or a crank.

#### Terraviper-5

#5
##### Feb 05, 2013, 08:45 pmLast Edit: Feb 05, 2013, 08:52 pm by Terraviper-5 Reason: 1

you need a H bridge that control by an opto couple then this could be use
btw the third leg is it connected to anything body or something

So actually I cant do anything with this circuit without h-bridge? Oh well. I have a lot of soldering to do then, 3 h-bridges >.<

I cant really see where it is going, its like the motor has 2 pins coming out of it, and ontop of them a small board with this connector has been soldered. I just connect power to original two pins and the motor spins (using Motor Shield R3).

I'll preface this with the disclaimer that I hate when people suggest changing my design instead of answering directly, but in the case of a bell, have you considered a mechanical oscillation method? Then you only need to move the motor in a single direction. Very, very simple.

An oscillation could be provided by a cam or a crank.

Yeah, but in this case it would be easier for me to make the motor do all the work, I dont have the necessary tools to make a mechanical solution, while I can quickly order some electrical components and solder up a electronical solution. I already have the wheel prepared, I will put a strap around it and on the other end put it around motor's axle. It will then spin the wheel in both directions (the wheel is that black thing on the picture).

#### Retroplayer

#6
##### Feb 05, 2013, 08:56 pm

Yeah, but in this case it would be easier for me to make the motor do all the work, I dont have the necessary tools to make a mechanical solution, while I can quickly order some electrical components and solder up a electronical solution.

Fair enough and I can understand. Realize that you will need to overcome momentum to reverse the motors. Technically, for a bell, all you need to do is drive in one direction, then let go. The bell will swing back by its own weight and up in the other direction. So, all you need really is to kickstart it in one direction and keep it moving.

Similar to a church bell, you could just affix a lever and a motor on a pulley. You drive the pulley in one direction, the bell lifts. Then let go of the motor at its highest point and the weight spins in it in the other direction. Sense when it is at its lowest point and kick the motor again.  Instead of sensing anything, you can just use timing.

If you really want to go with the astable multivibrator approach, why not just get rid of the micro altogether and use a 555 timer to directly control the motor?

My last suggestion.

#### Terraviper-5

#7
##### Feb 05, 2013, 11:06 pm

Fair enough and I can understand. Realize that you will need to overcome momentum to reverse the motors. Technically, for a bell, all you need to do is drive in one direction, then let go. The bell will swing back by its own weight and up in the other direction. So, all you need really is to kickstart it in one direction and keep it moving.

Similar to a church bell, you could just affix a lever and a motor on a pulley. You drive the pulley in one direction, the bell lifts. Then let go of the motor at its highest point and the weight spins in it in the other direction. Sense when it is at its lowest point and kick the motor again.  Instead of sensing anything, you can just use timing.

If you really want to go with the astable multivibrator approach, why not just get rid of the micro altogether and use a 555 timer to directly control the motor?

My last suggestion.

Yes, that's true, I could only spin the motor in one direction, but, especially with lighter bells, this results in uneven swinging because the motor is strong when it pulls the bell in one direction, then, when it releases, the bell swings back at lower speed because nothing is helping it. It also has to overcome the motor's friction (axle is not completely light to turn) which makes the swinging even more uneven. Sensing would be perfect, but as you say timing is good enough here, I intend to time the motor swinging with a potentiometer (trial and error) to get a perfect frequency.

Actually that is a great idea, I haven't though about that. Simply use 555 timer and avoid assembling the multivibrator. Excellent. I would still need the mcu to turn everyhing on and off though, it is connected to Chronodot RTC and controls at which hours bell will swing (and ring). The reason for multivibrator is that it makes setting the frequency and testing the bell mcu independent, and since mcu has limited number of pins, I can save one of them this way. At three bells that would mean using 3 instead of 6 pins, which is a lot for me.

#### Retroplayer

#8
##### Feb 06, 2013, 12:16 am
I do suspect that constant torque on the bell axle may dampen the ringing. A bell sounds its best when it swings loosely.

Well, you mention that you don't have the ability to make a mechanism, so how to you currently plan to actuate the bells with your motors?

#### Terraviper-5

#9
##### Feb 06, 2013, 01:59 pmLast Edit: Feb 06, 2013, 02:03 pm by Terraviper-5 Reason: 1

I do suspect that constant torque on the bell axle may dampen the ringing. A bell sounds its best when it swings loosely.

Well, you mention that you don't have the ability to make a mechanism, so how to you currently plan to actuate the bells with your motors?

That is true. That's why it would be best to either add a delay between when motor cuts off and when motor pulls in other direction or to make "soft edges" (slow the motor down before stopping it completely and then slowly speed it up again - with PWM). Not sure yet if I can do that with 555 timer, I saw a dimming LED effect on youtube, maybe it can be done for the motor too.

Yes, I maybe forgot to mention, but this steel frame was made in a factory with welding machine, I can only add/remove small things that are screwed onto the frame, not welded.
I intend to do it like this:

The wheel is made of plastic and I already have it, so basically I only have to add a strap and fixate the motor.

#### Uomotubo

#10
##### Sep 10, 2014, 03:29 pm
Hi! I'm trying to realize a project as yours! I know that it's been a year from your last post, but maybe you've figure out!!
This video is yours?