no idea what im doing.

ok. the furthest i have delved into electronics is computer repair and setup. i know a little about audio electonics, but only what i have been told. no "hands on" experience. that being said:

i would like to make a board that controls 4 motors. each motor needs to be able to move left or right and i would like the control of the motors to be dictated by pressing one button for right and one button for left. i would also like a wheel or button that controls the speed of each motor independently. this sounds so basic i feel stupid asking. but i saw some servos that were small enough for my project here:

http://www.junun.org/MarkIII/Info.jsp?item=16

but i dont understand how they are controled. do i need a servo control board? i saw a dc speed regulator here:

**broken link removed**

and am not sure if this would be a better way of controling the speed outside of voltage regulation. i dont know if this is even necessary. attached is the basic pic of what i want to accomplish. i know this is probably too trivial to be addressed by anyone, but if there are any ideas on which direction i need to go they would be appriciated. thanks!

~robbie

I suggest you tell us more clearly what you are wanting to do, as opposed to what you think you need to do it!.

Just so that you are not heading off in entirily the wrong direction, those hobby servos you linked to only have a 180 degree rotation. They won't go round and round...

i want the servos (or other suggested motors) to turn knobs. i want the knob being turned to move from 225 to 135 if zero degrees is on top(see pic below), so i guess the servos i found wont move that far.

i want the servos (or other suggested motors) to attach to the top of a knob(s) and move them to the right when one button is pressed and to the left when another button is pressed (see pic above for vague illustration :wink: ) but at a slow rate. like from 225 -> 135 would take about 3 seconds at maximum speed and about 15 seconds at the slowest speed. but i want the servo (or other motor) to to stop when the button is let go. i.e. it only moves when the button is depressed.

DirtyLude said:

Just so that you are not heading off in entirily the wrong direction, those hobby servos you linked to only have a 180 degree rotation. They won't go round and round...

Click to expand...

any ideas on where to find servos(other motors) that will move in the manner i want?

Those turning knobs, like on stereo's are usually controlled by stepper motors. Any regular gear motor would have a hard time when you tried moving the knob manually. Do you actually want to be able to read the position of the knob, or do you just want spinny dials?

I'm not certain how easy this would be using passives and standard logic chips. I know it would be fairly easy to do with a microcontroller.

Using a servo motor to turn a dial that could have been turned by hand seems really stupid. I think you have not given us the real story.

DirtyLude said:

Just so that you are not heading off in entirily the wrong direction, those hobby servos you linked to only have a 180 degree rotation. They won't go round and round...

Click to expand...

unless you mod them - pretty easy to do.

Russlk said:

Using a servo motor to turn a dial that could have been turned by hand seems really stupid.

Click to expand...

Russel,

Shame on you... Ham operators do this all the time... They put stepper motors (and limit switches) on large variable capacitors in a tuner that needs to be mounted at the base of an antenna in their back yards to allow remote control of the tuner from within their "radio shack"...

Kind regards, Mike

philba said:

unless you mod them - pretty easy to do.

Click to expand...

Yes, that's an option. Good point. As long as you wont be turning the wheels manually, that will work.

Mike said:

Russlk said:

Using a servo motor to turn a dial that could have been turned by hand seems really stupid.

Click to expand...

Russel,

Shame on you... Ham operators do this all the time... They put stepper motors (and limit switches) on large variable capacitors in a tuner that needs to be mounted at the base of an antenna in their back yards to allow remote control of the tuner from within their "radio shack"...

Kind regards, Mike

Click to expand...

you must be thinking old style there :lol:
We now are in 2006.

Forget about hooking up a motor to a control knob. Like Russlk said, it is stupid. Also, it is more expensive and more risky. Instead, you need a DAC. A DAC stands for Digital to Analog Converter.
What it does is convert a binary number (a number consisting of only 1's and 0's) to a voltage. The output of this voltage can be used to drive an H-bridge (a circuit that allows a motor to work with any circuit) and therefore drive a motor.
a DAC can be bought as a chip, or you can be like me, and make one yourself.

Also, take resolution into consideration. The higher number of bits you have in your DAC, the finer the resolution, and it will act as if it was a super-linear control, so linear, you wouldn't have done it with your setup of driving a knob with a motor.

and one more thing, a DAC, whether made by yourself out of discrete components, or using a DAC chip will take up A LOT LESS space than your current setup.

lol, that's old now too. You get a PWM chip or a microcontroller and skip the DAC altogether. Just PWM the HBridge.

Or in the case of driving a potentiometer, use a digital pot which, I think, has been mentioned before. totally non-mechanical.

:shock: ummmm.......

ok. i do live recording and would like access to my input/output knobs without having to dig around in the bag. so all i want is to be able to attach small motors the the existing knobs so that i can operate them while watching the show.

after looking at PWM's and microcontrollers they seem to do more than i want. all i need is to have the motor clipped on the knob and 3 buttons controlling the motor. one that "turns left", one that "turns right" and one that would probably be better as a wheel or knob that controls speed.

i dont want to replace the pots on my preamp due to voiding the warranty.

if using PWM's or microcontrollers will conserve a lot of space as mentioned above, then maybe that is the way to go. but what are my other options? like i said before i have little to no knowledge of this kind of stuff and would like the easiest route possible.

the servos i linked to before are about the perfect size for my project, so if they arent right to use, what is a better solution? how hard is it to mod the ones listed?

thanks for all the replies. this is going to be cool if i can figure it out. kudos to all

mstechca said:

Mike said:

Russlk said:

Using a servo motor to turn a dial that could have been turned by hand seems really stupid.

Click to expand...

Russel,

Shame on you... Ham operators do this all the time... They put stepper motors (and limit switches) on large variable capacitors in a tuner that needs to be mounted at the base of an antenna in their back yards to allow remote control of the tuner from within their "radio shack"...

Kind regards, Mike

Click to expand...

you must be thinking old style there :lol:
We now are in 2006.

Forget about hooking up a motor to a control knob. Like Russlk said, it is stupid. Also, it is more expensive and more risky. Instead, you need a DAC. A DAC stands for Digital to Analog Converter.
What it does is convert a binary number (a number consisting of only 1's and 0's) to a voltage. The output of this voltage can be used to drive an H-bridge (a circuit that allows a motor to work with any circuit) and therefore drive a motor.
a DAC can be bought as a chip, or you can be like me, and make one yourself.

Also, take resolution into consideration. The higher number of bits you have in your DAC, the finer the resolution, and it will act as if it was a super-linear control, so linear, you wouldn't have done it with your setup of driving a knob with a motor.

and one more thing, a DAC, whether made by yourself out of discrete components, or using a DAC chip will take up A LOT LESS space than your current setup.

Click to expand...

How do you marry a DAC (analog output) to an H-bridge (digital input)?

ok i found a related topic here

and i think the schematic posted by ron (just posted above) is about what im looking for. right?

if so, i have a few questions. i understand the PIC is a microcontroller. i dont understand what the driver is or what Vcc stands for... :?
any web resources about explaniations of schematics? books are good too, but cost $$ that i dont have

i totally feel rons response to that kid in the other post about not wanting to a)design this for him and b)this isnt a school and he should know some of this stuff. BUT i am being totally upfront about not knowing a damn thing about any of this. so i hope you all will humor me a little longer. :wink:

RC model Servos are very easy to control with a microcontroller. The driver is actually in the servo so all you need to do is send it pulses. As I recall, its a 20 mS window with a 1-2 mS wide pulse. 1.5mS being "neutral", 2 mS fully one way, 1 fully the other way. You could also use a 555 timer. google has lots of circuits for driving servos. Here's a nice little description (though they say a different pulse width) -

after more research i think ive switched gears(no pun intended). i am now thinking stepper motor (as suggested above) and controlling it with a basic stepper control board. is this the right train of thought?

You really need to do some studying. These URLs should get you started.

**broken link removed**
**broken link removed**
**broken link removed**

Russlk said:

You really need to do some studying. These URLs should get you started.

**broken link removed**
**broken link removed**
**broken link removed**

Click to expand...

thanks for the links. i will retire to the nerdery with my calculator. let you know when i get out......

I think this is absolutely the best stepping motor tutorial, bar none.
https://www.cs.uiowa.edu/~jones/step/

but, driving steppers is much more complex than driving an RC servo. If i was doing this project, I'd probably choose a servo. since the electronics to drive them is pretty simple.

do your research and come to your own conclusions but i think you might agree with me.