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Old 23rd October 2012, 05:50 AM   #1
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Default Upgrade belt drive TT by PLL circuit

Before this upgrading,I drived the platter by a deck motor.I dismantled the simple drive pcb from deck motor,and designed a PLL circuit to replace it.Here are some pics about this DIY:

circuit,PLL IC is SANYO LC7991M:
111.jpg

I etched the pcb by myself and soldered it:
20121020_211212-1.jpg

here is the speed photo sensor, black and white strips were atteched on the edge of platter:
PLL2.jpg

The green led will be lighted when the speed is within 33.33rpm+-6%
PLL3.jpg

The final speed is very steady through the control of error DAC in LC7991,test it by 50HZ strobe:
PLL4.jpg

Last edited by eaglebear; 24th October 2012 at 08:09 AM.
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Old 23rd October 2012, 05:26 PM   #2
Nanook is offline Nanook  Canada
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Default Nice to see...

I'm assuming an AC motor? Or Servo control DC motor?

This is a great project. It seems this is relatively simple project but, 6% error is pretty high. Tighter control (+/- .5%) might be a better goal.
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Old 23rd October 2012, 05:34 PM   #3
kevinkr is offline kevinkr  United States
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Eaglebear please post your attachments using the forum's server, and post an image of the schematic large enough that members can actually see it.

Interesting design.
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Old 23rd October 2012, 07:40 PM   #4
gk7 is offline gk7
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How did you etch the strobe markings ?
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Old 24th October 2012, 02:04 AM   #5
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Default large sch. pic.

2012-10-24 08 57 08.jpg
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Old 24th October 2012, 02:22 AM   #6
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Hi,nanook!(+-6%) is not the control error,the LC7991 control pins will directly pull high or low when the input signal is out of this range(100HZ+-6%,the crystal is 2.048MHZ,not 11.0592 as schematic),the inner DAC don‘t work.The final control precision is depend on the DAC output,I think the precision should be less than 1%.
Attachment is the datasheet of LC7991.

413-12368-0-LC7991M.pdf

Last edited by eaglebear; 24th October 2012 at 02:37 AM.
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Old 24th October 2012, 02:33 AM   #7
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Quote:
Originally Posted by gk7 View Post
How did you etch the strobe markings ?
Hi!gk7,I made the markings by pringting on paper in stead of etching directly,it's easier.

Drawing by CAD
qq.jpg
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