need help...

[dacflyer]

i have a few small dc hobby motors
3-6 volts...i am looking for a simple...
one pot and 1-2 transistor speed control<p>i am wanting to use this.in this way...<p>i have a 4017...want to use the outputs..to give the motor 10 different speeds...each speed will be preset by the pot...output from each speed controller will go thru a dioad then to the motor..<p>i am making a spirograph thingie...using 2 motors and mirrors...and a cheap lazer...i have controlled the motors before with a variable power supply... looks cool when i get the motor at just the right speed...and when i get to the next perfect speed i get another pattern,,, so i figgured if i can use a simple speed control...i can get 10 or more different patterns...knowhatimean ?
i just have to build a circuit times how many steps i want.... i can picture what i want,, just cannot think how to make it,,i know its easy for some brainiac out there... just 1 pot and 1-2 transistor speed control is all i need...thanx

[josmith]

DC motor speed is proportional to voltage so you want your transistor hooked up as a voltage follower and the pot hooked up as a voltage divider. <p>With a small motor you can get away with using just those two components.

[Edd]

Dacflyer de jetflyer:<p>A lot of variable unknowns weren’t mentioned, but conceptually , since you will be needing a power supply for the unit anyway, how about the utilization of a LM317 and driving its center adjustment input. That input will require some buffering between it and your 4017’s meager CMOS output level, typically a couple of bipolar xstrs in darlington connection to bring up that drive level. Meanwhile over at the 4017, dumping the outputs into as many 5 or 10 k ten turn trim pots so that the individual speeds could be easier adjusted in with the finer degree of adjustment provided by the ten turn range.Or if even more precise adjustment, trim into the proper speed and find the res of the two arms of the pot and sub fixed res of those values and drop in a 1k 10 turn trimmer at their junction ,thusly providing an even greater vernier adjustment range at that particular threshold. Each of the separate 10 outputs of the trim pots being taken out from the center terminal to the anode of an isolation/steering diode and then, all of the cathodes in common feeding the buffered stage prior to the ‘317. This would provide isolated and individual adjustment at each stage…..in preference to the technique of using a ladder/summation network of resistors with their touchy interreaction when trimming them all in.<p>On the motors lower speed range, if the lower output range of the 317’s 1.25v spec is a bit too high yet, use an appropriate current level of series diode to the motor…..then ¾ V would probably be at the stall range of it anyway, if any substantial torque was involved. I’m assuming you are using your motors to initiate a mechanical shift in your mirrors X and Y axis to produce a Lissajous pattern with your mirror reflected lasers beam….which should be able to present a multiple of patterns with harmonic and subharmonic interrelationships.
If not wanting to use the time tested LM317……another viable alternative for the motor driver circuit might be with just a few bipolars in a darlington configuration such as you can refer to in this site…
http://ourworld.compuserve.com/homepage ... tm#317.gif
See the fourth circuit down.<p>
73's de Edd
[email protected] ............(Interstellar~~~~~Warp~~Speed)
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[dacflyer]

edd, i am in awww about your knowledge !....
but i am a mere novice... is it possible to provide a diagram? i'd be most greatful... thanks buddy ! , oh great guru !

[Chris Smith]

Also try gluing a small chip of a mirror to a speaker and play music through it. Makes great light effects. Bumping the graphic equalizer settings also changes the patterns.

[Edd]

Dacflyer de jetflyer:
Find out the unknown variable. Specifically, hook up a motor in the physical mode that you will be using it in and then use your lab pwr supply to check out the current consumption of the motor at the lowest voltage that you are going to run it at and then the current at the highest voltage it is to be run and feed those four snippets of info back to me at the atti addee.<p>73's de Edd
[email protected]...(Interstellar~~~Warp~~~Speed)
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[dacflyer]

hey ed,,the motors are small cd spindle motors
and only have a 1" mirror glued to them,,and they are in the low low microamps..they typically ran off of 12volts,,
it seems once before i seen a speed adjust on a tape player motor once...and it had a small
2 transistor / 1 pot set up...but i cannot find none now,,Hmmm...well let me know what you think...

[gadgeteer]

I wouldn't use a linear device (transistor/lm317); motors suck current, so a linear controller will get very hot. Visit [url=http://www.mpja.com,]www.mpja.com,[/url] and buy one of his two motor-controller-kits, or build your own. Output a square-wave, and control the duty cycle (time on vs time off) to control speed.<p>RE speakers--- good advice. But take a first-surface mirror, long and skinny (and thin thickness-wise); attach one end to the center of the speaker, and the other end to the metal speaker FRAME, with daubs of silicon rubber caulking. As the speaker moves, your mirror moves in only one dimension --- generating a line with your reflected laser. Now build a SECOND speaker-mirror, and drive them with a STEREO SIGNAL. Bounce the laser off the first mirror, then off the second (the second oriented at 90 degrees from the first), and your stereo signal will paint complicated lisiduous waveforms {left channel controlling the vertical, right channel controlling the horizontal)...
<p>
...there is nothing wrong with your TV set; we are controlling the picture...

[josmith]

Meanwhile back on earth............
The only two good ways to regulate the speed of a motor are feedback or IR comp. Since the motors in question have no tach feedback and IR is only usefull to compensate for load changes all we have left is to regulate the input voltage to the motor. No matter how much you overkill the circuit that's still all you have.<p>Since the motor load is small any power transistor should be able to handle the load. So as interesting as all this other discussion is you asked for a one or two transistor regulator. The"Simple Adjustable Voltage Source" in ed's link would do fine.YOu might even eliminate one of the transistors in this circuit and use the first stage to drive the motor. Using a regulated power supply would be a good idea too.