DIY AC motor control - Page 7

makinson1 · 9th April 2008, 01:25 AM

Whatever you guys decide on, I hope it's cheap and will work with the 16 pole BIC motor in my project.

leadbelly · 10th April 2008, 07:22 PM

Everything discussed so far is too expensive or too hard for my tastes

Can it be simplified to the point where just a single LM1875 is set up as a Wein bridge oscillator driving a transformer? Is there a pitfall? I guess one question I have is the tracking error of a typical stereo pot (to vary the "R" and thus frequency) would result in oscillation.

leadbelly · 10th April 2008, 07:55 PM

Quote:

Originally posted by leadbelly
would result in oscillation.

I guess "instability" might be a better choice than "oscillation"

Pjotr · 10th April 2008, 08:35 PM

Tracking error of the tuning pot is no problem concerning stability. It only changes the loop gain somewhat but that is accounted for by the lamp stabilisation.

In my design the bridge was dimensioned by fixed resistors and the pot was just to trim de speed plus and minus approx 5 %. I have no drawn schematic of it, it was just build straight away. If it helps I can draw a schematic, but that will not exactly reflect the thing of 10 years ago. So some fine tuning/experimenting yourself is needed to get it working properly.

Cheers

leadbelly · 10th April 2008, 08:54 PM

Thanks. I actually forgot about your post. I saw this in a web search and I though it might be even better than using a lamp to stabilize the oscillator:

http://www.calvin.edu/~pribeiro/cour...ion-Darren.ppt

Michael Ando · 23rd April 2008, 01:27 AM

Hello Mark Kelly, I am trying to contact you regarding the power supply of my PT turntable. I am unable to sent you a PM on this board as I have not made previous posts. I believe you are a busy person but if you could contact me I would greatly appreciate it. I live not that far from Geelong in Lorne.
Apologies to people in this thread for this post but I couldn't think of another way of contacting Mark who I think looks at this board fairly regularly. Cheers Michael Anderson

Mark Kelly · 23rd April 2008, 08:10 AM

You have mail

KBK · 26th April 2008, 02:55 AM

Quote:

Originally posted by karvid

The base of the arm is a hair high and you need to give that cartridge a clockwise spin by about 1.5 degrees.

10th April 2008, 07:22 PM	#62
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	Everything discussed so far is too expensive or too hard for my tastes Can it be simplified to the point where just a single LM1875 is set up as a Wein bridge oscillator driving a transformer? Is there a pitfall? I guess one question I have is the tracking error of a typical stereo pot (to vary the "R" and thus frequency) would result in oscillation. __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

10th April 2008, 08:54 PM	#65
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	Thanks. I actually forgot about your post. I saw this in a web search and I though it might be even better than using a lamp to stabilize the oscillator: http://www.calvin.edu/~pribeiro/cour...ion-Darren.ppt __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

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10th April 2008, 08:35 PM	#64
Pjotr diyAudio Member Join Date: Nov 2002 Location: Netherlands	Tracking error of the tuning pot is no problem concerning stability. It only changes the loop gain somewhat but that is accounted for by the lamp stabilisation. In my design the bridge was dimensioned by fixed resistors and the pot was just to trim de speed plus and minus approx 5 %. I have no drawn schematic of it, it was just build straight away. If it helps I can draw a schematic, but that will not exactly reflect the thing of 10 years ago. So some fine tuning/experimenting yourself is needed to get it working properly. Cheers

23rd April 2008, 01:27 AM	#66
Michael Ando diyAudio Member Join Date: Aug 2007	Hello Mark Kelly, I am trying to contact you regarding the power supply of my PT turntable. I am unable to sent you a PM on this board as I have not made previous posts. I believe you are a busy person but if you could contact me I would greatly appreciate it. I live not that far from Geelong in Lorne. Apologies to people in this thread for this post but I couldn't think of another way of contacting Mark who I think looks at this board fairly regularly. Cheers Michael Anderson

23rd April 2008, 08:10 AM	#67
Mark Kelly diyAudio Member Join Date: Feb 2006 Location: Geelong	You have mail