Please make a drawing yourself and don't use a resistor but a resistor and a LED as it is useful to see if the PSU is working.
Just draw your favourite rectifier, a CLC filter and the datasheet circuit. No need for preregulation at all when transformer and regulator are carefully chosen. Try to draw it as neat as possible and then show it here and we will assist you. Benefit is that you learn from it too.
Do you really need 24V or will it be fed to various other regs?
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Hello Jean-Paul,
I bought a Sota bldc turntable motor that comes with a special kind of controller that is fed by a 24 volts 500mA switched power supply. A hand ful of parts in a plastic container plugged into the wall. Because they send me one only to be used for 115 volt i thought about making a simple linear power supply.
My idea was that this would result in a cleaner 24 volts and maybe it would also function as a kind of isolation between the digital controller and the rest of my gear.
Many times you read about these cheap switching power supplies messing up everything.
I read on this site about the lt3088 too. It needs less current to make it start working so to say.
Of course there will be no " ripple " left but people say that is important to focus on higher frequency garbage that can be dealt with by using the right value and the right kind of caps on the right stops. At the output and in parallel with the resistor that will determine the output voltage. Probably i am going to use a fixed resistor plus a pot in series. I have read that the value is rather high and it could be difficult to get one resistor that will give you exaxtly 24 volt.
Greetings,Eduard
I bought a Sota bldc turntable motor that comes with a special kind of controller that is fed by a 24 volts 500mA switched power supply. A hand ful of parts in a plastic container plugged into the wall. Because they send me one only to be used for 115 volt i thought about making a simple linear power supply.
My idea was that this would result in a cleaner 24 volts and maybe it would also function as a kind of isolation between the digital controller and the rest of my gear.
Many times you read about these cheap switching power supplies messing up everything.
I read on this site about the lt3088 too. It needs less current to make it start working so to say.
Of course there will be no " ripple " left but people say that is important to focus on higher frequency garbage that can be dealt with by using the right value and the right kind of caps on the right stops. At the output and in parallel with the resistor that will determine the output voltage. Probably i am going to use a fixed resistor plus a pot in series. I have read that the value is rather high and it could be difficult to get one resistor that will give you exaxtly 24 volt.
Greetings,Eduard
Are you sure the SMPS can not be used on 230V mains voltage (normally SMPS are usable from around 110 to 230V)?
I don't think you have to worry much about this motor controller as it is a 24V 3 phase generator. In this case I think the main goal is, as you said, to have less pollution of the mains voltage. A regulator should be chosen that can handle 40V. if you would choose a 24V transformer you are too close to the 36V maximum input voltage of LT3080. With a 22V transformer and an LDO like LT3080 it will be OK when you use somewhat large filter cap like a 10.000 µF 50V one. A heatsink will be necessary and there will be heat build up contrary to the SMPS.
I don't think you have to worry much about this motor controller as it is a 24V 3 phase generator. In this case I think the main goal is, as you said, to have less pollution of the mains voltage. A regulator should be chosen that can handle 40V. if you would choose a 24V transformer you are too close to the 36V maximum input voltage of LT3080. With a 22V transformer and an LDO like LT3080 it will be OK when you use somewhat large filter cap like a 10.000 µF 50V one. A heatsink will be necessary and there will be heat build up contrary to the SMPS.
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Another option is a 230V to 115V transformer (verhuistrafo) of let's say 50 or 100 VA. You can build one in a sturdy metal case with adequate filtering of the mains voltages which also prevents noise creeping back in the mains voltage. Connect the casing to PE, use fuses at both sides, use a sturdy power switch.
Normally one would prefer not to use a transformer but in this case it may have some benefits.
Normally one would prefer not to use a transformer but in this case it may have some benefits.
Hello,
I checked it is 120 volts 60 hertz . I have gone to my stock of similar supplies and this is the only one that is not universal!
The ldo you mention is 20,5 volt maximum.
Most solution have a limited number of parts. The stand by / on switch is on the controller so the power supply can be made pretty basic.
First i came across the 7824 but then you read about more sophisticated devices that dont cost a leg.
Maybe a 7824 with the right output cap and the unit installed at a few cm from the controller wil be more than enough.
Greetings,Eduard
I checked it is 120 volts 60 hertz . I have gone to my stock of similar supplies and this is the only one that is not universal!
The ldo you mention is 20,5 volt maximum.
Most solution have a limited number of parts. The stand by / on switch is on the controller so the power supply can be made pretty basic.
First i came across the 7824 but then you read about more sophisticated devices that dont cost a leg.
Maybe a 7824 with the right output cap and the unit installed at a few cm from the controller wil be more than enough.
Greetings,Eduard
7824 is not low drop so it needs 27V as a minimum at the input. You then need a 24V transformer that in practice puts out way more than 24V.
Let's do some assumptions:
26V x 1.41 = 36,66V. Minus 2V diode drop = 34,66V. I keep it simple and let ripple not play a role for now. 34,66V - 24V = 10,66V.
10,66V x 0,5A = 5,33W dissipation or simply put: heat. That means a larger heatsink and a ventilated casing.
Always use a real power switch so you are sure things are truly off the mains when you leave your home. Certainly with DIY stuff (insurance).
If we would know how critical the stuff in the controller is there would be more possibilities. If it is a circuit with its own regulators for the sensitive electronics just needing approx. 24V for the 3 phase output I would don't hesitate to use a 18V transformer (after a mains filter), a rectifier and overdimensioned CLC filtering and no regulation at all. Just overvoltage protection at the mains side with a fuse. Simpler, less heat and you will meet the goal in a way.
Again, only if the inverter in the controller is not too critical with regards to exact voltage. Most inverters aren't but yours might be the exception.
Can you post a picture of the 24V SMPS?
Let's do some assumptions:
26V x 1.41 = 36,66V. Minus 2V diode drop = 34,66V. I keep it simple and let ripple not play a role for now. 34,66V - 24V = 10,66V.
10,66V x 0,5A = 5,33W dissipation or simply put: heat. That means a larger heatsink and a ventilated casing.
Always use a real power switch so you are sure things are truly off the mains when you leave your home. Certainly with DIY stuff (insurance).
If we would know how critical the stuff in the controller is there would be more possibilities. If it is a circuit with its own regulators for the sensitive electronics just needing approx. 24V for the 3 phase output I would don't hesitate to use a 18V transformer (after a mains filter), a rectifier and overdimensioned CLC filtering and no regulation at all. Just overvoltage protection at the mains side with a fuse. Simpler, less heat and you will meet the goal in a way.
Again, only if the inverter in the controller is not too critical with regards to exact voltage. Most inverters aren't but yours might be the exception.
Can you post a picture of the 24V SMPS?
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Hello Jean-Paul,
I opened up the 9 volt supply that is used for the speed control display. It is just a transformer, four diodes and a 1000 microfarad 16 volt cap.
The 24 volt supply is indeed a smps supply doesnt look a high grade supply.
I already do use symmetrical power supply with Lundahl LL1662 transformers. But the turntable supply will be connected to the same LL1662 as my phono pre amp and my line pre amp so i think going for some kind of 24 volt basic style regulation would be better than SMPS which i believe are only used to reduce weight and dimensions.
In the manual of the '' motor controller '' it says 24 volts 500mA nominal. Maybe it can be taken care of the same way as the 9 volt supply. BUT i dont wanna take a risk. Suppose i would go for a basic CLC supply and there is/are indeed a kind of regulator inside. The voltage drop across L in standby mode could be almost zero resulting in an overvoltage for the regulator. I will try to find a safe way by finding the right transformer and possibly a Clc or CRC network with some extra DCR to keep the input voltage for the 7824 well within limits. I remember Guido Tent once gave me the tip to install a high power zenerdiode to limit the inputvoltage on the regulator.
Greetings, eduard
I opened up the 9 volt supply that is used for the speed control display. It is just a transformer, four diodes and a 1000 microfarad 16 volt cap.
The 24 volt supply is indeed a smps supply doesnt look a high grade supply.
I already do use symmetrical power supply with Lundahl LL1662 transformers. But the turntable supply will be connected to the same LL1662 as my phono pre amp and my line pre amp so i think going for some kind of 24 volt basic style regulation would be better than SMPS which i believe are only used to reduce weight and dimensions.
In the manual of the '' motor controller '' it says 24 volts 500mA nominal. Maybe it can be taken care of the same way as the 9 volt supply. BUT i dont wanna take a risk. Suppose i would go for a basic CLC supply and there is/are indeed a kind of regulator inside. The voltage drop across L in standby mode could be almost zero resulting in an overvoltage for the regulator. I will try to find a safe way by finding the right transformer and possibly a Clc or CRC network with some extra DCR to keep the input voltage for the 7824 well within limits. I remember Guido Tent once gave me the tip to install a high power zenerdiode to limit the inputvoltage on the regulator.
Greetings, eduard
You can feed the regulator output through a capacitor to an amplifier like an opamp and boost the signal so it can be seen. In fact I believe there are specialist PSU 'scope and SA probes you can buy to do this specifically for analyzing supply voltage quality.
Might be a neat project to make one, perhaps with a video-bandwidth opamp as the active part and some protection on the input for when the capacitor is first connected to a rail.
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