Bambozi Power Supply

[Ayne]

Below in the picture is my idea to construct the power supply.

Out Puts
+5V
+9V
+2 to +35V
GND
-5V
-9V
-2 to -35V

Sin Wave Genrator 100Hz TO 1MHz.
The problem is, i don't know that which type of Oscillator i need to use.

Sqr Wave Genrator 100Hz TO 1MHz.
The problem is, i don't know that which type of Oscillator i need to use.
Will LM555 timer will work???

Displaying Unit,
There should be a displaying unit for displaying the frequency of Signal gernators and out put voltage coming from power supply. But i not know how can i show them on 7Segment Display.

Thermal Protection,
There should be a thermal protection circuit, Need Help.

Short circuit Protection,
A short circuit protection circuit, Need Help.

I want to Build, not to buy.

And Plz guide me for more improvement.
Is there need for adding some thing more???
Thanks.

 

[Nigel Goodwin]

Below in the picture is my idea to construct the power supply.

Out Puts
+5V
+9V
+2 to +35V
GND
-5V
-9V
-2 to -35V

Sin Wave Genrator 100Hz TO 1MHz.
The problem is, i don't know that which type of Oscillator i need to use.

Wien bridge!.

Sqr Wave Genrator 100Hz TO 1MHz.
The problem is, i don't know that which type of Oscillator i need to use.
Will LM555 timer will work???

Use the sine oscillator above, and square it - either an overdriven amplifier or a schmitt trigger.

Displaying Unit,
There should be a displaying unit for displaying the frequency of Signal gernators and out put voltage coming from power supply. But i not know how can i show them on 7Segment Display.

Use an LCD text module driven by a PIC, you can display all you need on one display.

Thermal Protection,
There should be a thermal protection circuit, Need Help.

The regulators you've suggested are already thermally protected, just make sure you mount them on suitably sized heatsinks.

Short circuit Protection,
A short circuit protection circuit, Need Help.

Again, the regulators are already S/C protected, suitable heatsinks needed as above.

I want to Build, not to buy.

And Plz guide me for more improvement.
Is there need for adding some thing more???
Thanks.

Personally I'd suggest building the signal generator and PSU in seperate boxes - it's more versatile.

 

[Hero999]

Below in the picture is my idea to construct the power supply.

Out Puts
+5V
+9V
+2 to +35V
GND
-5V
-9V
-2 to -35V

What current?
I assume you want 1.5A for the variable positive and negitive supplies and 1 A for the fixed supplies.

What power?

Is it important to you be able to run all the outputs at their maximum currents simultaniously?

This will require quite a large transformer.

Sin Wave Genrator 100Hz TO 1MHz.

What output impedance? 50ohms is the norm.

The problem is, i don't know that which type of Oscillator i need to use.

I'd go for a wein bridge oscillator, but you'll need to switch the capacitors around and you'll need a fast op-amp.

Sqr Wave Genrator 100Hz TO 1MHz.
The problem is, i don't know that which type of Oscillator i need to use.
Will LM555 timer will work???

The TS555 will bo all the way up to 2.7MHz

What about protecting the output form short circuits?

Do you what to be able to adjust the duty cycle?

Would you even like to be able to adjust the duty and frequency seperately?

If so then a schmitt trigger oscillator and comparator is probably a better option.

Displaying Unit,
There should be a displaying unit for displaying the frequency of Signal gernators and out put voltage coming from power supply. But i not know how can i show them on 7Segment Display.

You mean a frequency counter?

Wouldn't it be even better if you had the option to isolate it from the sig gen so you can use it seperately?

You can build a frequency counter from discrete logic, programmable loge or even a PIC. The choice is yours.

Thermal Protection,
There should be a thermal protection circuit, Need Help.

Short circuit Protection,
A short circuit protection circuit, Need Help.

The regulator IC have this built in. However if your transformer and rectifiers can't supply enough current to power all the output simultaniously then you'll a fuse on the DC circuit, it's probably best to use a pollyswitch for this as replacing it everytime you over load it will be a pain. Anyway I'd but a suitable slow blow fuse in series with the live/phase/hot line connected to the transformer's primary just in case.

I want to Build, not to buy.

It's certainly possible, but it will depend on your level of experiance, how many projects have you built before?

I certainly haven't built something as complex as this in one go.

And Plz guide me for more improvement.
Is there need for adding some thing more???
Thanks.

I would build this up section by section not all in one go. I'd build the simple power supplies first then add on everything else later. The only thing is I'd make sure the case is big enough and leave room for the other componants. Sometimes the hardest part of a project is fitting the darn thing into the case!

 

[Ayne]

Thanks

What current?
What power?
Is it important to you be able to run all the outputs at their maximum currents simultaniously?
This will require quite a large transformer.
What output impedance? 50ohms is the norm.

I need 1A current on both side(+,- V).
currents will be simultaniously...
I have 35-35Volts center tape transformer rated current on it is 2A.

I'd go for a wein bridge oscillator, but you'll need to switch the capacitors around and you'll need a fast op-amp.

Will TL072 Work???
I need out put impedance 100hm:

The TS555 will bo all the way up to 2.7MHz
What about protecting the output form short circuits?
Do you what to be able to adjust the duty cycle?
Would you even like to be able to adjust the duty and frequency seperately?
If so then a schmitt trigger oscillator and comparator is probably a better option.

Can u help me for protecting output from short circuit???
Yes i want to like to adjust the duty and frequency seperately, Guide me more.
Plz help me with tutorials or any web link

You mean a frequency counter?
Wouldn't it be even better if you had the option to isolate it from the sig gen so you can use it seperately?
You can build a frequency counter from discrete logic, programmable loge or even a PIC. The choice is yours.

Yes a frequency counter and a voltage measurer circuit
I think that PIC is a best choice but i am not a good programmer. I only know the MikroBasic and i have made some little programs like LED flashing etc.
Needed help.
Will PIC16F876 will work???
As u r saying use seperately than how is possiable to use same PIC for measuring Voltage and frequency??

The regulator IC have this built in. However if your transformer and rectifiers can't supply enough current to power all the output simultaniously then you'll a fuse on the DC circuit, it's probably best to use a pollyswitch for this as replacing it everytime you over load it will be a pain. Anyway I'd but a suitable slow blow fuse in series with the live/phase/hot line connected to the transformer's primary just in case.

My transformer is rating is 35-35Volts 2A, I think it will work with no problem.
I will also add a Fuse in series with the live/phase/hot line connected to the transformer's primary.

It's certainly possible, but it will depend on your level of experiance, how many projects have you built before?

I already had made power supplies with LM317 and LM7805 seperately.
My main purpose of making this supply is combining all thing in one box with digital display.

 

[audioguru]

Your 35VAC transformer will produce an unregulated output of 47VDC which is much too high for the regulators. Their max is 35VDC and 40VDC. It would also create too much heat in the regulators.

The LM7805, LM7905, LM7809, LM7909, LM317 and LM337 cannot supply their full 1A with a high voltage across them because they will be too hot. They automatically reduce their max output current to about 300mA to protect themselves, then shutdown if they get too hot.

The TL072 has a max output swing up to only 100kHz.

 

[Nigel Goodwin]

Yes a frequency counter and a voltage measurer circuit
I think that PIC is a best choice but i am not a good programmer. I only know the MikroBasic and i have made some little programs like LED flashing etc.
Needed help.
Will PIC16F876 will work???

Yes, that would be fine.

As u r saying use seperately than how is possiable to use same PIC for measuring Voltage and frequency??

As you would in any PIC program, do them sequentially.

Start:
Read and display voltage1
Read and display current1
Read and display voltage2
Read and display current2
Read and display frequency
Goto Start

Obviously though, if you were building the PSU and generator in seperate boxes you couldn't use the same PIC and display, and would require seperate ones in each unit.

 

[Hero999]

I need 1A current on both side(+,- V).
currents will be simultaniously...
I have 35-35Volts center tape transformer rated current on it is 2A.

You really need a 28V-0-28V transformer, either that you you could try building a 39V pre regulator using a transistor and zenner but this isn't an ideal solution.

Also consider using an LM317 and LM337 in place of the LM7809 and LM7909, the LM7805 and LM7905 can then be connected internally to the output.

Also please note that the voltages on the transformer secondary and from the output from the supply are hazardous and are above the legal in the UK and Europeean limits for allowing physical contact with. The IEEE regulations state that in dry contitions user contact shall be avoided with voltages greater than 25VAC and 60VDC. On your poposed project the secondary side of your transformer gives 70VAC, 98VDC on the output capacitors and 70VDC on the output.

I would lower the maximum output to +-30VDC and use a 24V-0-24V 2A transformer, there will still be hazardous voltages in the case but at least the output will be relativity safe. Be aware that 60VDC is the maximum and is only considered safe in dry conditions, it is high enough to give you a fair shock if you have wet skin.

Will TL072 Work???
I need out put impedance 100hm:

As audioguru says, find a faster op-amp, pay particular attention to the slew rate as well as the unity gain bandwidth.

Alternatively, you can get ICs function generators to make square, triangle and sinewaves. If you can find and old ICL8038 then great it will work up to 200kHz but it's no longer made, however there is the new MAX038 which goes up to 20MHz but it's expensive. Forget about using it upto said fequency and expect the PIC to count it, but there's always the option of adding a divide by 10 counter. Personally I'd prefer the challenge of desigining my own.

Can u help me for protecting output from short circuit???

Like I said before, the regulator ICs will protect against that, but for extra protection you should add a 2A polyswitch in series with both outputs from the transformer secondary.

Yes i want to like to adjust the duty and frequency seperately, Guide me more.
Plz help me with tutorials or any web link

The best way would be an oscillator with a 50% duty cycle using the TS555 and then connect the timing capacitor to one input of a comparator and vary the reference voltage on the other pin. You'll now have one output with a variable duty cycle and another with a fixed duty cycle.

This is quite an easy circuit to make but what sort of output do you need? Just 5V or something more exotic? It could be variable but 5V is normally adequate.

I only know the MikroBasic and i have made some little programs like LED flashing etc.

That's more than I know but it doesn't sound too difficult.

In general I think you need to consider what you need rather than what you want. How many circuits have you built or even wanted to build that require a bipolar 5V, 9V and 35V power supply?

Probably not that many.

A positive and negitive 15V supply is probably more than good enough for most applications. Perhapps you could make do with a positive and negitive 2 to 15V supply or a bipolar variable power supply like the one I've built.

https://www.electro-tech-online.com/threads/variable-bipolar-power-supply.24291/

I agree a separate 5V output or even bipolar output is always handy though for powering TTL or CMOS circuits but I wouldn't normally need anything more.

As for a signal generator, do you really need a 1MHz sinewave? Normally 20kHz is more than enough, 100kHz normally being the max for testing audio amplifiers with.

Google be your friend, there is a wealth of information out there. If you can't find what you want then try narrowing your search criteria, broadening it or trying various keywords and synonyms.

 

[Nigel Goodwin]

Forget about using it upto said fequency and expect the PIC to count it, but there's always the option of adding a divide by 10 counter.

You're obviously not familiar with PIC's?, a PIC running at 4MHz can accurately read frequencies as high as 50MHz - it's a VERY common project, and there's even a very old MicroChip application note on doing just that with an old OTP PIC. There are also plenty of modern versions, using newer FLASH/EEPROM devices, and LCD displays rather than LED's - EPE even did one earlier this year!.

 

[Hero999]

How does that work?

Just thinking, can't the PIC be used as a low frequency pulse generator and sinewave generator too? If so hwat are the typical frequency limits? Somehow I can't see you been able to generate a 1MHz sinewave with a PIC!

 

[Nigel Goodwin]

How does that work?

You use the internal 16 bit counter/timer fed from an external clock - the PIC merely reads the value from the hardware counter - the clever part is reading the upper 8 bits, as they are not addressable.

These PIC frequency counters generally auto-range, on lower frequencies they auto-switch to period measurement to keep accuracy high, and display refreashing fast.

Just thinking, can't the PIC be used as a low frequency pulse generator and sinewave generator too? If so hwat are the typical frequency limits? Somehow I can't see you been able to generate a 1MHz sinewave with a PIC!

Not that high no, but you can get reasonable audio frequencies, check out **broken link removed** which does upto 60KHz sinewave using just a PIC. To be honest, that's probably as high as you need?, mostly it would be for audio anyway.

 

[Ayne]

I have another 30-30Volts transformer. it is in my audio amplifier. will this work?

 

[Nigel Goodwin]

For the lower voltage supplies you need a lower voltage input - do the maths for the dissipation in the regulators - it's dead simple.

W = V x I

Assuming I (current) is 1A, and assume a 5V regulator (ignoring any over-voltage concerns).

Your rectified DC voltage will be about 45V - subtracting the 5V output leaves 40V to be dropped across the poor little 7805 regulator, so W = 40 x 1, giving 40W of heat to be dissipated by the 7805. I'm not bothering looking the specs up, because 40W is obviously FAR too high for such a little device.

 

[audioguru]

A little 7805 will be at its max rated temperature if it has an infinite (perfect) heatsink and only 20W of dissipation.

Maxim's MAX038 function generator is also not made anymore.

 

[Ayne]

How can i solve the problem,
I have 30-30V transformer and i can't buy another transformer.
But i want to made a power supply as above.

 

[Nigel Goodwin]

Unless you go the switch-mode route, then there's no escape - you HAVE to dissipate the heat somewhere. You could fit very high wattage resistors between the supply rail and the regulators - but this just moves some of the heat from the regulator to the resistors, and the resistors will be expensive and need mounting on heatsinks.

Assuming all outputs are fully loaded you're probably talking about 200W or so of heat to get rid off - so huge heatsinks and cooling fans are likely to be essential!.

Far easier (and cheaper) to have an extra mains transformer that feeds the low voltage regulators. At the risk of repeating myself?, it might also be a good idea to make the variable and fixed supplies in different boxes, for added versatility - don't forget, there's no need for a voltmeter on the fixed supplies.

 

[Hero999]

Maxim's MAX038 function generator is also not made anymore.

Are there any good waveform generator ICs that are still made?

But i want to made a power supply as above.

The problem is what you want to do isn't really practical.

What you want to do is build a linear power supply with a high voltage input and low voltage output on lowest setting. Linear regulators drop the voltage by converting the excess energy to heat so a large voltage drop will generate a lot of heat and require a lot of cooling.

Don't worry there are solutions to this:

You could lower the input voltage on lower settings. A good way of doing this is to use a transformer with a tap in the middle and run it at half the input voltage for lower voltage settings. Unfortunately you need a positive and negitive supply, so you'd need a transformer with two 28V-0-28V windings.

You might want to consider using a switching regulator. There are specialised ICs that can do this or you can use the LM317/337 with a few other componants (see datasheet). The problem is this is often harder to build (apart from some ICs) and the output is always more noisy than a linear regulator.

I suggest you use a combination of both techniques. This is know as a hybrid regulator. The idea is you use a switching regulator to drop the most voltage followed by a liner regulator to smooth the output resulting in a happy medium. You could use the 35V transfomer to get a -48 to 0 +48V supply, then regulate it down to 3V or 4V greater than the output setting (depending on how noisy it is). This could be done by either having two voltage ranges or using a subtractor circuit.

Personally I wouldn't bother becuase this is getting too complex. I'd be satisfied with having a more sensible (lower) output voltage.

 

[Ayne]

With some Changes,
I found a transformer from backyard of 45-45 volts center tape 4 Ampere transformer. I opened it and reduce it's turns and add two more windings on it.
After rewinding now it's Specification,
With No Load,
Two windings of 34-34 Volts,
Two windings of 14-14 Volts.

Now my questions,
Will this work??

When we will convert these AC voltage into DC then what will be the output DC voltages???

 

[audioguru]

The peak voltage of a sine-wave from a transformer is its RMS voltage times the root of 2 (1.414). So 34VAC has a peak voltage of 48.0V which is reduced by the rectifier bridge to 46.6VDC. It will be higher without a load.

The max voltage for 78xx regulators is 35VDC and the max across an LM317 is 40V. At these very high voltages they will get too hot and reduce their output current then shut down.

14VAC has a peak voltage of 19.8V which is reduced by the rectifier bridge to 18.4VDC. It will be higher without a load. With pretty big heatsinks, a 78xx or an LM317 will produce an output current of about 1.0A. With a lower input voltage they would have an output current of 1.5A.

 

[Ayne]

It mean i need to rewind my transformer to reduce more turns of transformer's winding.
It means transformer specification should be,
1. Two winding of 24-24 volts RMS for producing 34 of Peak voltages and rectifier will convert them in 30 Volts Apporx.

2. Two winding of 10-10 volts RMS for producing 14 of Peak voltages and rectifier will convert them in 12 Volts Apporx

Am i right???

 

[audioguru]

It mean i need to rewind my transformer to reduce more turns of transformer's winding.
Am i right???

The regulators reduce their output current when there is more than 15V across them. Their max heating is only about 20W before they shut down.
If you add current-boosting power transistors to them then they won't limit the current and won't shut down.