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how to control speed of a small dc motor used in cd player

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rajaram04

rajaram04

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Hello sir
I wish to make a speed control circuit for a small dc motor already used in a dvd or cd player
so what must be the circuit diagram & what basic components & proper power supply i need here to operate motor with such cicuitry,please tell everything in detail with circuit diagram
Thanks
 

You can search related material in google by searching "dc motor control using hall sensor and H-bridge" or other variants.
If you tell more about the application and how you are controlling speed, will clear more your problem?
 

I guess, this is a BLDC (3 phase AC) rather than DC motor.
 

okk sir but h bridge is used set directions & hall sensor u told is for brushless motor n i didnt find any circuitry there . Now i want control the speed of it with no load n full load too . i made an assembly on a disk containing lights & battery with a circuit so i want to make the the moves of disc very slow so as to present the effect of light i designed & i made two more removing unit which requires the slow movment sir & its all for my research on communication purposes so please enable me the proper circuit to make control over it . I saw dc motors used in taperecorder mechanism . it has a built in speed control system but its not working with any device except that particular . so i need a separate circuitry for it so as to control speed as per my requirment sir . . please help
thanks
 

With no speed control, what revs per minute (RPM) is your motor running at?

I can let you know how to do speed control of a motor. But I need to first know how controllable it is. Is the motor on a geared assembly?
 

No sir the motor is single one & no gears are around or inside it . Its just a simple motor basically used for rotating a cd in a cd player n likewise 3 motors are used in cd loader unit,i fetch out the motor n working on it its too small one n inside it it only has a three poll coil surrounded by a ring shaped maget stick to the inner walls of motor body same as in a dc motor used in taperecorders etc . I dont know how to determine the r.p.m. sir & too it is not mentioned on it , please tell me how can i get you the info.you are asking above sir ? below im sending you the picture of a motor just having same resemblance with mine it is exactly that motor.i found it on google
91_1340235507.jpg
 

Straight forward I can suggest you, derive PWM signal and control the motor form this. hall sensor is very good but your application is limited only, so better you go for H-Bridge architecture.
If you are doing it for learning purpose, I suggest you to come up with block diagram. Then one by one you define the specification for your each of the blocks.
I can hint-out that it needs, Clock (Oscillator), it need control signal derived from motor speed, and driver stage, may be simple MOSFET.
 

It's not clear from the photo if it's a conventional brushed DC or a BLDC with build in electronics. But this doesn't change much to the control options.

In my view, a simple linear motor controller, as used in cassette players would be appropriate if low circuit complexity is an objective. But it also depends on the intended speed sensing method. In a CD player, disk speed can be sensed indirectly through the data channel, without a dedicated speed sensor.
 

sir its just a simple motor with no labelling but was when installed already in a cd player loader it has a disc on it on which the cd was driven out . all that mechanism was damaged so i take this motor out n supplied a 3.6.v from Ni-cd battery n found the speed optimum to use it anyway but it was too fast as i was unable to control it . when you told about the H bridge i followed but it was for direction purpose but not the speed . tell me how to find out voltage & current required by the mototr or say a universal methhod to determine the parameters for a given motor , here im showing you the simple assembly general sketch to show how i want to use it for the load . have a look




else nothing in it sir cause rest of the electronics built inside the 100 gms aprrox disk will do its work but i need simply handle the speed of this motor individually . please reply
 

One hint, you give pulsed supply to your dc motor, if it runs faster control the duty cycle.
 

You're right. Since you dont need to control the direction, you dont need the H-bridge.

A simple 555 based PWM circuit should work fine.

**broken link removed**

Regards,

Anand Dhuru
 

Yesssssssssssss thats what i want actually sir but as today is my musical show so have to move now & ll doo practicals next day , sir please tell me a substitute for IRFZ46N cause i just called in the shop but they didn't heared about it so its unavailable finally we can say . . please let me know about what i ve to implant there . . . .thanks a lot:)
 

I suggested using the CD driver because you will learn more by reverse engineering the existing design of a working CD player. trace signals and schematic. then cut out essential parts. Given that you have not provided any part number, we can only guess what might work best, not what is working and why it works is your learning process.
 

hmm thanks the idea is nice but the problem is how to study the mother board containing chips only & how to study the pin configurations ? now i ve to implant all the assemble of a new cd player cause its very difficult to get a separate driver & as i ve to install so many communicating system for my practicals so i ve to install that much number of cd players also . Too my units are to be installed outside the atmosphere then i ve to make much much protection against climate in comparision to my previous case of single motor. so now the work is going in complications & a little bit harrasing for me to work lonely in my practicals . i too ve to cover a big space . . so i ve to go for some other ideas sir to operate simply the speed of a given dc motor . sir would you please tell me hoe to determine the r.p.m. of a motor ?
 

Wiki says The drive motor (also called spindle) rotates the disc between 200 and 500 revolutions per minute.
But it could be made to run faster or slower.

Rajaram can you clearly state your purpose;
Function:
Control:
Qty to make:
Environment:
Other factors.:
Budget:
Time factor:
 

sir it emplyos many uses & techniques & so many things & i ve to do it in a small budget cuase i dont have any financially sound atmosphere still im a student & trying to work for the sake of mankind within reasonable budjets so as to support people above & below poverty line . sir i cant explain everything in detail cause its only a first step to a new era very honestly & i really need your help from very basics of electronics . If i can start my first step then i can explain you only the direction where im moving . Now only just i can tell that its related to communication by spreading & gathering of electron to make spiral elctromagnetic transmission.I don't know whthr im moving in a right direction but my first move deals with control of motor speed thats only a baby step to my research work :) thanks for all your support it really motivated me a lot in 3 days only sir
 

Sir may i know about the problems facing by science in the field of A.I. (Artificial Intellegence) ?

- - - Updated - - -

Function: to rotate a disc contaning electronics producing infra red & electromagnetic waves
Control: speed of diffrent 7 motors individually
Qty to make: 7 for now
Environment: in outside the building or in open area & to be implanted any where with no relation with each other for now
Other factors. : may be also used for decorative items in festivals but not so clear thats not main motive
Budget:as much as less possible . sir the new motor cost is 30/- here & used motor cost is only 10/- so u can imagine now
Time factor : unlimited presently or may be vary in future :)
 

That motor looks like just a very basic DC motor that might run on a few volts.
To vary the speed, use the 555 in the astable circuit configuration and stick the output to the motor. If you need a bit more power, then
connect the 555 to a single transistor as a buffer.

I think you can do 90% of "beginners" electronic "things" if you spend a bit of time playing with a 555, an op-amp and a few discrete
components. Study the wikipedia pages on PWM, 555, op-amp and you'll be able to do 90% of beginners stuff.

It would be good if you can read a beginners practical book too - I'd suggest the art of electronics but it's not cheap. An alternative
would be the Forrest Mims books, if you can find them, or Bernard Babani.
 

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