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Simple DC motor control

Hi guys, just discovered this thread when i was looking for a dc/series type speed controller PCB or kit,(so I am a bit behind the curve!)may i ask if there are there any more of those speed controller PCB(s) left sir?

REGARDS

JOHNY
 
Hi, I wonder if after all this time you would still have any boards or know where I could get one for the turntable motor controller. Any assistance would be appreciated. Kind regards Geoff. [email protected]
 
Hello ,

I'm new here , following the simple DC motor control topic for some time now .
I gathered the info as much as possible and went to build it on a eurocard printboard
with soldering islands . here's where I am right now :

Motor Maxon A-max 110173 . 8,26 Ohm DCR
NPN : TIP31C
Opamp : TL071CN
47K for both R43 & R44
R45 target somewhere between 22K & 24K . using a 50K trimpot
R46 at 2,7 Ohm
R38 & R39 at 2K2 . using trimpot as well
Zener 8.2 Volt
Transformer 13 Volt - 0 - 13 Volt ( 0.2 A ) AC terroid
PR trimpot 10K ( no series resistors ) Single adjusting string for 33RPM only .


It works a charme in therms of adjusting unloaded motor speed , and see the circuit is working when loading the motor spindle with my finger ;) .. i.e. output voltage increasing
when load applied .

Here some questions :

How do I choose motor pulley diameter / ratio .. in respect to voltage ? I assume I should
aim for lowest motor RPM ( mech noise ) ?

Also : I can't find any PS schematic ?? I know it's a simple one , but perhaps I'm missing some
important things at this one ?

Hopefuly someone is able to put me on the richt track with this . another thing I need to do is printing the strobe disk etc.
Well , it has been a real joy to build so far .. time to move on and get the whole thing driving my platter someday soon .

Thanks in advance ,

Paul
 
The pulley sizes are up to you.... It's motor dependent.

The board from the group-buy contains everything bar a transformer, so the PS question is somewhat moot.

Paul
 
Hi Paul ,

Thx for reply ! what about the board ? I haven't seen any details of the ps layout or circuit .. perhaps I have overseen things .. not very likely :)

Anyway .. I got over some issues here relating to pulley diameter etc. i.e. manufactering a few myself on my minilathe .. bronze and brass .

THX
 
Yes I got it but I've just had a tooth out so concentrating on staunching the flow of blood right now. Will respond soon
 
Hi there, I have just discovered this thread and would really like to get my hands on one of the boards plus a copy of the BOM. Can anybody help please? As a novice to this (and any other for that matter) Forum, I apologise if I am trampling over any protocols. Thanks, Richard.
 
Hi there, I've juste discovered this thread, and would be very interested in building one of these Motor controller by myself, and I don't know if anyone got the pcb design (Gerber files???) of the motor controller wich can work wth 12v motor from promtec (cause I'm a little stuck to make it).

thanks
 
There was and is no pcb available; the 3 or 4 prototype PCBs a sympathetic friend had made on the margin (quite literally) of a much larger project are all long gone.

This remains an experimental (and unoriginal) circuit that can be built easily, dead-bug style on a bit of veroboard. Since the circuit is strictly low frequency and heavily filtered, layout is exceptionally uncritical. The suggested schematic is in the first post in thread. Add a large (100-1000uF, 16v) capacitor across Rs (Werner's commutation filter) - it helps enormously.

It is quite a tweaky thing to play with; worst case if for some reason you cannot get your TT speed stable to your satisfaction is just to short-out the one current-sensing resistor i.e. replace with a wire link. The board then reverts to a simple discrete low-noise voltage regulator - i.e an open-loop controller switchable between two speeds (DC supply voltages on the output). It's maybe 15-20dB 'quieter' than simply using an LM317.
 
Reading through this gave me and idea to try a TPR4 using both sections and
powering a motor from the differential of the two sections.

They'll drift uniformly so once set, should stay within very precise limits.

What do you think Martin.?
 
I think the major problem is the motor rather than the supply voltage itself.

Doing what Linn appear to do with the Radikal and timing each revolution, then adjusting motor voltage to get and keep the average speed right, would seem to be a sensible approach. Not exactly expensive either with an Arduino or similar and off the shelf sensor. Trickiest part might be controlling the voltage, perhaps you can just put a chunky emitter follower on a DAC pin and drive it directly. Or interfere with the 'adj' on a 317.

Paul
 
I still think the answer is to avoid the mechanical commutation and just drive a brushless motor instead. Several ways to do that from very analogue (3-phase oscillator+ 1 IC power amps - add a voltage-frequency converter and 'pull' the oscillator' if you want analogue feedback) to essentially digital methods.

Simple DC motors are attractive for DIY experimental reasons being cheap, readily available, easy to play with - but a long way from 'easy to finesse'.
 
Doing what Linn appear to do with the Radikal and timing each revolution, then adjusting motor voltage to get and keep the average speed right, would seem to be a sensible approach. Not exactly expensive either with an Arduino or similar and off the shelf sensor....
The hard part is measuring the rotation. Measure once a revolution and you can only have a time constant of about 5 seconds. Ok for long term stabilty but not for drag due to modulation, warps etc.
If yo could find a way of putting a strobe marking around the platter, then the loop can be much faster. The challenge is that this pattern must be very uniform
 


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