I am looking in two different directions at getting a good 3 phase, low distortion signal source.
Digital, using 3 x Analog Devices LD9833 DDS signal generator modules, these should allow frequency variation control of as little as 0.004Hz steps.
This will need a xtal controlled master clock, along with a fair bit of low level programming, something I haven't done for many years, but which will allow me to pass the long winter hours
Analog, using a low distortion oscillator followed by a 3 phase splitter.
This is a much simpler scenario, which I am confident will be more than adequate for the single frequency generator that I am planning. It will unfortunately get a bit more complex if 2 or more output frequencies are needed.
I'll post updates as and when they arise, in the meantime please keep posting any useful ideas.
Digital, using 3 x Analog Devices LD9833 DDS signal generator modules, these should allow frequency variation control of as little as 0.004Hz steps.
This will need a xtal controlled master clock, along with a fair bit of low level programming, something I haven't done for many years, but which will allow me to pass the long winter hours
Analog, using a low distortion oscillator followed by a 3 phase splitter.
This is a much simpler scenario, which I am confident will be more than adequate for the single frequency generator that I am planning. It will unfortunately get a bit more complex if 2 or more output frequencies are needed.
I'll post updates as and when they arise, in the meantime please keep posting any useful ideas.
ESP - Sinewaves
This should work if wanting fine control. You can even adjust one side only to get 45 RPM with a higher output. That is change one side with double RC value you would if doing both sides. It should mimic the motor inductance quite well. Do the wrong side to drop the voltage. I have done that over a 1:3 range without problems. If TL074 318K 10 nF is workable for 50 Hz.
This should work if wanting fine control. You can even adjust one side only to get 45 RPM with a higher output. That is change one side with double RC value you would if doing both sides. It should mimic the motor inductance quite well. Do the wrong side to drop the voltage. I have done that over a 1:3 range without problems. If TL074 318K 10 nF is workable for 50 Hz.
Anyone try the EXAR XR2206 oscillator based kits from eBay? It seems to have all the controls one would need and the XR2206 specs aren't bad. Add a 90 degree phase shift circuit for the second coil and a LM3886 chip amp or old stereo amp plus two transformers and you would have a inexpensive, good performing power supply.
Hello,
as this means power amplifiers driving inductive loads, one should be aware of the need for free-wheel-diodes. Thorens were not, hence a child was able to blow the motor amplifier of one of their Mark IV models by stopping and turning the running platter by hand. I fitted 1N4007 in order to allow for excessive child play.
Furthermore Thorens used BC546/7/8/556/7/8 transistors with maximum current of 100mA, while nominal motor current was already 60 or so mA. So i exchanged them for BC327/337.
Uli
as this means power amplifiers driving inductive loads, one should be aware of the need for free-wheel-diodes. Thorens were not, hence a child was able to blow the motor amplifier of one of their Mark IV models by stopping and turning the running platter by hand. I fitted 1N4007 in order to allow for excessive child play.
Furthermore Thorens used BC546/7/8/556/7/8 transistors with maximum current of 100mA, while nominal motor current was already 60 or so mA. So i exchanged them for BC327/337.
Uli
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These kits are brilliant and at very low cost. Stabilty is said to be 10ppm/C, or 10 times better than the VPI ADS.
Hans
Hey Guys
These new ideas and parts is great. We gone down two paths one where we needed 2 phase and the other with 3 phases. I went down the 3 phase path so I could try many different motors.
Without help with this transistor stuff I am pretty much in the dark. Anyone with ideas on signal generator which can create 2 or 3 phases throw up a schematic. If is not a ton of money I will build it and test it out.
We ran into a little brick wall for the guys who can not make pulleys or modify them. And it would be nice to fine tune for other variables that create small rpm changes.
I think it is great everyone is willing to push forward and see what we can come up with.
Enjoy the ride
Tom
These new ideas and parts is great. We gone down two paths one where we needed 2 phase and the other with 3 phases. I went down the 3 phase path so I could try many different motors.
Without help with this transistor stuff I am pretty much in the dark. Anyone with ideas on signal generator which can create 2 or 3 phases throw up a schematic. If is not a ton of money I will build it and test it out.
We ran into a little brick wall for the guys who can not make pulleys or modify them. And it would be nice to fine tune for other variables that create small rpm changes.
I think it is great everyone is willing to push forward and see what we can come up with.
Enjoy the ride
Tom
Hi Tom,
Here is an example of a generator kit XR2206 Function Signal Generator DIY Kit Sine Triangle Square Output 1HZ-1MHZ Sale - Banggood.com
and here is the design of a phase splitter.
The example is for 50hz in and 90 degrees shift, but I can give you the values for 60 Hz in and 60, 90 and 120 degrees out.
The op-amp can be any low cost version.
You can vary the 50Hz frequency for +/- 0.9 Hz, while the phase only shifts +/- 1 degree, almost negligible.
For two phases you need one opamp and for three phases two of them.
Hans
Hi Hans
They do not spec how fine of a frequency change this will do. So if I understand this the unit provides us the sine wave we need but does not have any phase splitting ability. So you build a circuit with the right values to get to 90 for the 2 phase unit and 2 generators with 2 circuits at 120 and 240 for 3 phase unit.
So if this thing can make small enough frequency changes I am all in. No real expense just a lot of solder time. I enjoy these kind of journeys.
If you could do a schematic for a 60hz 90 degree for my hurst motors and the combo schematic for the 2 generator 120 /240 splitter I would appreciate it.
Thanks Tom
They do not spec how fine of a frequency change this will do. So if I understand this the unit provides us the sine wave we need but does not have any phase splitting ability. So you build a circuit with the right values to get to 90 for the 2 phase unit and 2 generators with 2 circuits at 120 and 240 for 3 phase unit.
So if this thing can make small enough frequency changes I am all in. No real expense just a lot of solder time. I enjoy these kind of journeys.
If you could do a schematic for a 60hz 90 degree for my hurst motors and the combo schematic for the 2 generator 120 /240 splitter I would appreciate it.
Thanks Tom
Hans, great info, thank you very much. I would like to build a 60hz three phase version of what you have proposed. The values would be much appreciated.
I'm at a loss when it comes to solid state, I'm a self taught hollow state guy (vacuum tubes), however I am capable, and more than willing to go down this path. Let me see if I have this right.
First I build the XR2206 kit, then I build a three phase splitter, and use the signal from the kit to drive the splitter. This would give the ability to fine tune the frequency +/-0.9 hz, which I could use to fine tune speed, after getting it very close by mechanical means. It would also stabilize the frequency, once set, it should stay that way. Correct?
Any big changes in platter RPM, such as going from 33.33 to 45 rpm would be done by mechanical means, which I can do, as I haven't built my turntable yet. It'd be great to change platter speed from 33.3 to 45 by frequency alone, but I can deal with the mechanical option. Would it be possible to build a second kit and splitter for 81hz, to deal with electronically changing speeds, with the throw of a TPDT switch? Certainly seems cheap enough.
If you give me a schematic with values I will build it, and post back. Since I'm a complete dolt when it comes to solid state, could you be so kind as to identify suitable op amps?
One final question. How fine are the adjusting steps in that +/- 0.9 range? Thanks so much for your input on this. I think it is getting very close to a very nice solution to speed control for my 3 phase motor. Like you said it is a pity the 3 phase ebay generator is not ready for prime time.
twystd
I'm at a loss when it comes to solid state, I'm a self taught hollow state guy (vacuum tubes), however I am capable, and more than willing to go down this path. Let me see if I have this right.
First I build the XR2206 kit, then I build a three phase splitter, and use the signal from the kit to drive the splitter. This would give the ability to fine tune the frequency +/-0.9 hz, which I could use to fine tune speed, after getting it very close by mechanical means. It would also stabilize the frequency, once set, it should stay that way. Correct?
Any big changes in platter RPM, such as going from 33.33 to 45 rpm would be done by mechanical means, which I can do, as I haven't built my turntable yet. It'd be great to change platter speed from 33.3 to 45 by frequency alone, but I can deal with the mechanical option. Would it be possible to build a second kit and splitter for 81hz, to deal with electronically changing speeds, with the throw of a TPDT switch? Certainly seems cheap enough.
If you give me a schematic with values I will build it, and post back. Since I'm a complete dolt when it comes to solid state, could you be so kind as to identify suitable op amps?
One final question. How fine are the adjusting steps in that +/- 0.9 range? Thanks so much for your input on this. I think it is getting very close to a very nice solution to speed control for my 3 phase motor. Like you said it is a pity the 3 phase ebay generator is not ready for prime time.
twystd
Here are the splitters at 60Hz for resp 90, 120 and 240 degrees.
When switching to 81 Hz (=45 RPM) all you have to do is to change R9, R5 and R8 into a 1.35 lower value, so resp 7k46 and two times 10K3.
This can easily be achieved by switching a parallel resistor of resp 23K0 and two times 39K8 to R9, R5 and R8.
Hans
When switching to 81 Hz (=45 RPM) all you have to do is to change R9, R5 and R8 into a 1.35 lower value, so resp 7k46 and two times 10K3.
This can easily be achieved by switching a parallel resistor of resp 23K0 and two times 39K8 to R9, R5 and R8.
Hans
Stability of the chip is at 10ppm/C, so I think stability won't be an issue.
Just change the frequency and the phase splitter resistors, no mechanical adjustment is needed.
A NE5532 is a cheap and perfect amp for the job.
I have no idea what pot is used, but when fine adjustement is still too coarse, you could replace the pot by a 20 turn pot.
Hans
Thank you Hans, I can't tell you how much I appreciate the info. I will proceed with the project. I'll have to wait to the first of the month to buy the stuff, because of financial considerations, but I will proceed with this and report back. Tom, if you're monitoring this and decide to proceed, please keep us posted.
twystd
twystd
Hi Twystd
Looking up how the pin out and schematic correlate on the ne5532 op amp. There is 8 pins on that op amp???
So I am all in. Will order the parts I need today. Looks like at least one guy in states that has the gen kit for sale.
Hans is a class act for starting this thread and staying with it. For tube guys like us it is invaluable. I am enjoying learning more about this transistor stuff. Antek in the states has good deals on transformers if you still are going to change them.
Enjoy the ride
Tom
Looking up how the pin out and schematic correlate on the ne5532 op amp. There is 8 pins on that op amp???
So I am all in. Will order the parts I need today. Looks like at least one guy in states that has the gen kit for sale.
Hans is a class act for starting this thread and staying with it. For tube guys like us it is invaluable. I am enjoying learning more about this transistor stuff. Antek in the states has good deals on transformers if you still are going to change them.
Enjoy the ride
Tom
Yeah, I agree, Hans really is a class act, as the Aussies say, "good on ya mate!" Since this is so cheap to do, looks like I'm going with 2 generators and splitters. One for 33.33 RPM and the other for 45 RPM. Hopefully I'll play around with them, and get them dialed in, then just leave them. I think that will keep me from having to fool around with the pots when changing speed. I'll just switch back and forth from the 2 sources, to drive the amps and transformers.
Who is the source for the domestic supplier of the gen. kit? As far as transformers go, I've already ordered some 30VA R cores from ebay, they supposedly have Japanese steel cores, and an electrostatic shield between the primary and secondary. I'll wire them for 15V:230V, that should show a reflected impedance of 6.12 ohms to the amps, once the cores are energized. Cheap enough at $68.40 for 3 delivered. Unfortunately the proverbial "slow boat from China" delivery speed, hopefully worth the wait.
Here's a link to the NE5532 data sheet. http://www.ti.com/lit/ds/symlink/ne5532.pdf Looks like a dual op amp chip. I guess I'll have to use 2 chips with one section not hooked up for a 3 phase unit, one op amp chip only necessary for 2 phase. If I go with the two gen/splitter option looks like I can use the unused section, and fully utilize 3 chips. I'm of course not real familiar with the solid state side of things, but looks like we might have to have a dual rail 12V supply to run the op amps as well.
If I'm on the wrong track I urge anybody to straighten things out. To take a term from my old surfer days....I'm really stoked about this project!
twystd
Who is the source for the domestic supplier of the gen. kit? As far as transformers go, I've already ordered some 30VA R cores from ebay, they supposedly have Japanese steel cores, and an electrostatic shield between the primary and secondary. I'll wire them for 15V:230V, that should show a reflected impedance of 6.12 ohms to the amps, once the cores are energized. Cheap enough at $68.40 for 3 delivered. Unfortunately the proverbial "slow boat from China" delivery speed, hopefully worth the wait.
Here's a link to the NE5532 data sheet. http://www.ti.com/lit/ds/symlink/ne5532.pdf Looks like a dual op amp chip. I guess I'll have to use 2 chips with one section not hooked up for a 3 phase unit, one op amp chip only necessary for 2 phase. If I go with the two gen/splitter option looks like I can use the unused section, and fully utilize 3 chips. I'm of course not real familiar with the solid state side of things, but looks like we might have to have a dual rail 12V supply to run the op amps as well.
If I'm on the wrong track I urge anybody to straighten things out. To take a term from my old surfer days....I'm really stoked about this project!
twystd
Hey Twystd
Search EBay xr2206 function generator kit. There are a lot of them. Look at the 10 dollar ones and check seller location. The one I ordered was from tom tom out of New Jersey.
Looking at the schematic Hans drew I do not see a power supply you are referring to just 3 connections. While on the subject of our lack of knowledge on transistor stuff wonder what wattage the resistors need to be???
Regards Tom
Search EBay xr2206 function generator kit. There are a lot of them. Look at the 10 dollar ones and check seller location. The one I ordered was from tom tom out of New Jersey.
Looking at the schematic Hans drew I do not see a power supply you are referring to just 3 connections. While on the subject of our lack of knowledge on transistor stuff wonder what wattage the resistors need to be???
Regards Tom
Tom, got the source on the gen., thanks. If you look at the third page of the spec sheet you will see pin 4 is marked Vcc- and pin 8 is marked Vcc+ in the table right below the pinout on the same page it says pin 8 positive supply, and pin 4 negative supply. On the 4th page of the spec sheet table 7.3 gives the recommended voltage at 5-15 volts positive and negative. I just figured that it would be appropriate to use a 12V supply because I thought they'd be readily available, could be wrong about that though, as I haven't found a suitable supply yet. I learned a painful lesson by buying a single rail positive supply for my amps that I used in the first iteration of this project, they required a 50V dual rail supply, 50V+ and 50V-.
I'm thinking that Hans probably assumed we knew we would need a supply, so didn't include it in the schematic, but I could be wrong about that too. Kind of painful for a couple tube guys trying to deal with solid state. maybe one of the solid state guys will take pity on us, and straighten us out. Onward through the fog!
twystd
I'm thinking that Hans probably assumed we knew we would need a supply, so didn't include it in the schematic, but I could be wrong about that too. Kind of painful for a couple tube guys trying to deal with solid state. maybe one of the solid state guys will take pity on us, and straighten us out.
Onward through the fog!twystd
Hans, I've been looking over your schematic. Since I want to use 3 phases to drive a delta wound 3 phase motor, I can just not build the 90 degree phase leg, correct? Also, shouldn't R9 be 10k4? If I understand this correctly, I just take my feeds from the 0, 120, 240 legs, for my A,B, and C phases. Also I think (but not sure) I have to power the op amps with a + and - supply. I found a + and - 9v regulated supply on ebay LM7809 LM7909 ±9V Dual Voltage Regulator Rectifier Bridge Power Supply Module | eBay I have a 115/13V 15VA torroid laying around. I think I could power both the op amps and the generator with that supply. Am I on the right path?
twystd
twystd