If you still want to generate 24VAC direct to the motor without transformers, you can look at an amp based on the TPA-3255 IC. It can handle up to 50VDC. Most of the ready built amps are BTL type, so it will be able to produce 24VAC undistorted. You will need a 36 or 48VDC supply to power the amp.
You could also use step up transformers (12V-115VAC) with your current design with step down transformers (115-24VAC) to the motor. I doubt that you could find 12V-24VAC transformers.
You could also use step up transformers (12V-115VAC) with your current design with step down transformers (115-24VAC) to the motor. I doubt that you could find 12V-24VAC transformers.
Hi All
Big thanks to everyone for all the info that enabled me to do this project.
I have just completed the SG-4, and all tested good until I connected the TDA7492 amp as per Pyramids instructions (single phase 230v output).
I used an 80va torroidal transformer, I had available.
It has 2 x12v & 2 x 115 windings, connected as Pyramids diagram.
The problem I have is:-
Sometimes when I switch from standby or between 33 & 45 rpm the amp seems to go into overload, shunting on and off, not reaching the correct output voltage, or taking about 5 seconds to settle at the correct output.
The signal from the SG-4 looks good when this happens (925mV and a good sign wave), so I don't think its a fault on the SG-4.
Could it be the torroidal I am using?
Any ideas anyone?
Big thanks to everyone for all the info that enabled me to do this project.
I have just completed the SG-4, and all tested good until I connected the TDA7492 amp as per Pyramids instructions (single phase 230v output).
I used an 80va torroidal transformer, I had available.
It has 2 x12v & 2 x 115 windings, connected as Pyramids diagram.
The problem I have is:-
Sometimes when I switch from standby or between 33 & 45 rpm the amp seems to go into overload, shunting on and off, not reaching the correct output voltage, or taking about 5 seconds to settle at the correct output.
The signal from the SG-4 looks good when this happens (925mV and a good sign wave), so I don't think its a fault on the SG-4.
Could it be the torroidal I am using?
Any ideas anyone?
What sized motor are you driving?
In my experience, the larger the transformer rating, the more sensitive the amp is to sudden changes, both frequency and amplitude. If you have a 10W motor, then you don't need a transformer any larger than 15-25VA. Class D amps like the TDA7492 are especially sensitive; they have an overcurrent detect that shuts down the amp with very little delay, so they shut down even if the perceived overload barely crosses the threshold.
In my experience, the larger the transformer rating, the more sensitive the amp is to sudden changes, both frequency and amplitude. If you have a 10W motor, then you don't need a transformer any larger than 15-25VA. Class D amps like the TDA7492 are especially sensitive; they have an overcurrent detect that shuts down the amp with very little delay, so they shut down even if the perceived overload barely crosses the threshold.
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Yes. A large xfmr has a large core, therefore higher core hysteresis and losses when abrupt changes are made. It also has lower inductance and the amp will see a lower impedance when making sudden changes in amplitude or frequency. Either go to a 25W toroid, or use a larger amp that has a higher overload threshold.
Hi Pyramid
Just to let you know what happened when I tried a 60va transformer.
I have tried a 60va Torroidal transformer with 2 x 18v windings just to see the result, because I had it to hand.
With TDA amp output set at 920mV input 12v output:-
The amp did not go into overload shutdown, worked correctly.
So I decided to increase the amp input (from 920mV to 1.7V) to give approx 18v output to supply the new transformer.
Result - The amp did not go into overload shutdown, worked correctly.
So I connected the deck, Result - The amp did not go into overload shutdown, worked correctly.
I cannot find the spec for the TDA amp.
Do you think the amp will be ok with the higher input voltage, It does not get any hotter than at the lower input voltage.
Has anyone used this amp with a 60w transformer?
Just to let you know what happened when I tried a 60va transformer.
I have tried a 60va Torroidal transformer with 2 x 18v windings just to see the result, because I had it to hand.
With TDA amp output set at 920mV input 12v output:-
The amp did not go into overload shutdown, worked correctly.
So I decided to increase the amp input (from 920mV to 1.7V) to give approx 18v output to supply the new transformer.
Result - The amp did not go into overload shutdown, worked correctly.
So I connected the deck, Result - The amp did not go into overload shutdown, worked correctly.
I cannot find the spec for the TDA amp.
Do you think the amp will be ok with the higher input voltage, It does not get any hotter than at the lower input voltage.
Has anyone used this amp with a 60w transformer?
This is what I’ve bought, hope it’s correct
Hi Bill and all forum members,
This is the amp I bought:
TPA3255 Digital Power Amplifier Class D Audio Amp Assembled Board 300W&300W HiFi | eBay
And this is the PSU:
AC-DC Inverter 100-265V to 36V 5A Switching Power Supply Adapter SMPS Module | eBay
Hope it’s correct to power directly without transformers a 24v motor.
Regards,
Jorge
Hi Bill and all forum members,
This is the amp I bought:
TPA3255 Digital Power Amplifier Class D Audio Amp Assembled Board 300W&300W HiFi | eBay
And this is the PSU:
AC-DC Inverter 100-265V to 36V 5A Switching Power Supply Adapter SMPS Module | eBay
Hope it’s correct to power directly without transformers a 24v motor.
Regards,
Jorge
See my posts to jcastellano prior to yours.
The TDA7492 is rated for 24VDC supply max. It can only produce ~17VAC without distortion. An 60VA 18VAC xfmr will output 21-22VAC no load and will require 21-22VAC to produce 115VAC at the primary (no load). If you are getting 18VAC at the output of the amp, it is probably clipped and resembles a squarewave. Even with 18VAC input to the toroid, you will not get 115VAC at the primary.
My suggestion: Use a 25VA 12VAC toroid. If you choose not to, you are on you own.
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Hi Bill, need your experience based advice. Got uP all is works perfectly fine. Installed encoder and power consumption jumped from 65 to 175mA. Rotation functions (as up and down) are not works. Took out flipflop and current dropped back to 65mA. I assume that my chip is DOA or I damaged it during soldering (my chip is CD74HCT74E). Have you saw such behavior? Does it make sense to use CD4013 and not CD75HCT type?
I just wanted to express my gratitude to Bill for everything he has done to offer this project to the DIYAudio community. Thank you for your continued support and guidance with this and all your projects. It would have been easy to retire and move on to other things. Instead, you are here giving even more to the community than you had with your excellent commercial products. My little experimental system is finally back up and singing like it never has before with the completely rebuilt front end. Thank you.
Attachments
I have just connected the Arduino rotary encoder & Pcb. all works fine if the encoder is turned slowly.clockwise = up / anti-clock = down frequency.
If I turn it fast or flick the encoder as fast as I can - the frequency keeps going as if the up/ down push button is pressed.
To stop the the frequency counting I just have to turn the encoder one notch.
Interestingly if I flick it fast clockwise the frequency decreases. anti-clock the frequency decreases.
But turning the encoder slow it works correctly. clockwise = up / anti-clock = down frequency.
Anybody come across this problem.
If I turn it fast or flick the encoder as fast as I can - the frequency keeps going as if the up/ down push button is pressed.
To stop the the frequency counting I just have to turn the encoder one notch.
Interestingly if I flick it fast clockwise the frequency decreases. anti-clock the frequency decreases.
But turning the encoder slow it works correctly. clockwise = up / anti-clock = down frequency.
Anybody come across this problem.
Hello Cyber5,
I have encountered this frequency run issue but maybe not under the same circumstances as yours. My experience was when everything (or most of it) was laid out in test mode and not into a proper chassis. I also fitted a solid aluminum knob pulled from some old amplifier. The rotary encoder is the common type and unbranded out of China. What happen is all of a sudden it can do a frequency run and I've to quickly twist the encoder to stop it. I immediately suspected its either the 4013 chip (most unlikely) or some defect of some sort with the encoder itself since I don't expect that part to be of the highest quality for that price. I deduced that at some point of time, the knob or some internal play within the encoder is causing a sudden run. Since I mounted everything on a make do chassis, replaced the rotary encoder, this have not recurred. Meanwhile, I've placed order for a high quality replacement Bournes encoder of the similar specs and size to swap the China made encoder. I can't be too trusting on such parts which can underperform or fail for any reason. I hope not to encounter such a problem again after this.
I have encountered this frequency run issue but maybe not under the same circumstances as yours. My experience was when everything (or most of it) was laid out in test mode and not into a proper chassis. I also fitted a solid aluminum knob pulled from some old amplifier. The rotary encoder is the common type and unbranded out of China. What happen is all of a sudden it can do a frequency run and I've to quickly twist the encoder to stop it. I immediately suspected its either the 4013 chip (most unlikely) or some defect of some sort with the encoder itself since I don't expect that part to be of the highest quality for that price. I deduced that at some point of time, the knob or some internal play within the encoder is causing a sudden run. Since I mounted everything on a make do chassis, replaced the rotary encoder, this have not recurred. Meanwhile, I've placed order for a high quality replacement Bournes encoder of the similar specs and size to swap the China made encoder. I can't be too trusting on such parts which can underperform or fail for any reason. I hope not to encounter such a problem again after this.
Hi Coolmaster
Thanks for your quick reply. I have changed the rotary encoder for another Arduino rotary encoder and still getting the same problem.
I will do as you have and order a quality encoder, can you please post a link to the Bourns encoder you have ordered.
In the mean time I will look at your other suggestions, but I am wondering if the 4013 IC is faulty.
Also wondering about an Optical Encoder.
Thanks for your quick reply. I have changed the rotary encoder for another Arduino rotary encoder and still getting the same problem.
I will do as you have and order a quality encoder, can you please post a link to the Bourns encoder you have ordered.
In the mean time I will look at your other suggestions, but I am wondering if the 4013 IC is faulty.
Also wondering about an Optical Encoder.