ive got a dc motor and gear unit that i plan on using in my mod. i just need to find out some information about it. is there anyway to find out the voltage of the motor so i wont burn it out, or are there some kinds of standards for this? the unit came out of an old vcr, its a loading motor that moves the tray for the tape. any information on this would help me out. thanks.
Most motors in VCR's run at 5VDC. That in mind, Test it at 5V, if it seems to turn REALLY SLOW or not at all, Up the voltage and try again.. Most of the time, you can run a 5V motor at 12V for a short burst without burning it up... It's the current that you have to be careful of, since the only part that is being touched by the voltage is the brushes, and the coils. Too much power to the coils and you will heat it up, and possibly melt the plastic or even the coils themselves. Best to put it behind a heavy pot for testing, and start low in the voltage range. If you have enough power at 5V, go for it... I am using a 12Vmotor at 5V to move my Stealthed Baybus, if I run it at 12, I could lose a finger. no joke.
thanks for the info. i hooked it up to my 5vdc and ran it. thought it was going good till i remembered i have it resisted to run at 3.5vdc. it was running pretty good at 3.5vdc, but i wont know for sure until i build the complete unit, but now it looks pretty good. if its a bit slow, i can work with the gears or just have to wait a bit longer. does under voltage or under current hurt a dc motor?
No, But if you had a motor controller and like a stepper motor, underpowering can be fatal... Check this drive motor controller, from a PC with a 90W power supply, with a cd burner and 2 hard drives on a 933mHz P3...
can you post some pics of your motor in action? I am also thinking of doing something .......similar.
i cant at the moment sorry. i need to borrow a digicam, and build the darned thing first. but ill tell you this: the idea is to have a cd-rw in my mod that is hidden, when i push a button, said motor will raise the front of the rom out of the case (basically tilt the drive up) and allow me to load discs. then punch the button and down she goes.
just an addition to that underpowering thing... for the motor you have(which is a DC motor w/ field coil) it is impossible to damage it by underpowering it. Since it is basically a stator winding around a rotor, the amount of voltage determines the electromagnetic force applied to turn the rotor. Hence, the only problem you will have is with too much voltage, which as stated above, can damage the motor. Also, using a variable resistor to control speed of the motor is a very inefficient way of doing this. While it works, it generates heat, and by doing so, wastes power. A much better way of controlling the speed of your DC motor is with pulse width modulation. It controls the motor speed by driving the motor with short pulses. These pulses vary in duration to change the speed of the motor. The longer the pulses, the faster the motor turns, and vice versa. Here's a schematic of a pulse width modulation control circuit: R1 = 1 Meg 1/4W Resistor R2 = 100K Pot C1 = 0.1uF 25V Ceramic Disc Capacitor C2 = 0.01uF 25V Ceramic Disc Capacitor Q1 = IRF511 MOSFET (can substitute IRF620 if you need more than 5A) U1 = 4011 CMOS NAND Gate S1 = DPDT Switch M1 = Motor MISC =Case, Board, Heatsink, Knob For R2, Socket For U1
oh yes, just a side note about the schematics above, if you absolutely need more than 6V, add it in right before the switch
as an added extra bonus, there is a single IC that will PWM your DC motor, all you add is a 10k pot, and you're in control, and the cost is less than buying all the others seperate, also much smaller design, and easier to work with. Only thing is it's current limited (so is the PWM in the diagram) to around .5A, which on a 12VDC motor, should be plenty, depending on what you want to use it for, and my guess is that it's not rated for more than that since it comes from a VCR.
What is the IC's number, and can you boost it's output with a transistor or MOSFET (even though a mosfet is a transistor too)
thats good info to know. i wont need to control the motor indepenantly on this project. if i did, i woulda just stuck in some variable resistors. this portion of my mod i expect to run on 5vdc. the reason i had it running on 3.5vdc is becuase i used a switch box that i constructed for another project and just forgot there was a resistor in it. the whole time the motor will run depends on how fast it moves the cd-rw. i dont expect this to be more than two seconds. it just has to move it up enough to allow loading of the cds. since its just gona run on 5vdc, or very close to that, it shouldnt cause me any problems right? i like conkbot would also like to know what the ic number is just in case i need something like this in the future. crap, i just thought, do i need one of these controller circuits to reverse the motor? to make the cd-rw go down?
