Techniques... Making a Dual Supply from a Single Supply

[Ayne]

I want to know the techniques,
How can we make Dual supply from Single supply???

I mean i have Regulated 5 Volts coming from LM7805 and i want to convert these voltages into +9 * 0 * -9...

Infact i need this supply for OPAMPS... as we know our common OPAMP UA741 and TL072 works on Dual power supply... And i want to connect OPAMP output to PIC ADC...

I have seen Nigels analog board but he use IC and that IC is not available in our local market...

Thanks...

 

[Nigel Goodwin]

I want to know the techniques,
How can we make Dual supply from Single supply???

I mean i have Regulated 5 Volts coming from LM7805 and i want to convert these voltages into +9 * 0 * -9...

Infact i need this supply for OPAMPS... as we know our common OPAMP UA741 and TL072 works on Dual power supply... And i want to connect OPAMP output to PIC ADC...

I have seen Nigels analog board but he use IC and that IC is not available in our local market...

That IC is the most commonly available one you will find, if you want 5V to +/-9V you need to be looking at a switch-mode module - these are fairly easily available, but a LOT less so than the 7660 used in my tutorial.

 

[kchriste]

I have seen Nigels analog board but he use IC and that IC is not available in our local market...

Look for the ICL7662 or Si7661. They can directly replace the 7660 used on Nigels page. You can also do it with a 555 timer, some diodes and capacitors.

 

[Blueteeth]

Add to the above those DC-DC convertor modules, at around 1UKP (for a dual output, 5v -> +/-9v). Also some switchmodepower supply IC's can provide dual rail output with a small transformer, but thats probably overkill for your app.

If you just want the dual supply for opamps, dealing with AC (no DC offset) then you could just boost your 5v to something like 10v with a small switching capacitor regulator, and split that for a virtual ground. Not ideal, but for AC only signals, it'll work, you just need to remember to DC bias the output so its centred at 2.5V.

Sorry if I'm confusing you here, just sperting out idea's, the above posters have probably the easiest solution, and a 555 timer circuit does work, with shottky diodes it gives around -4V.

What sort of signal are you measuring with the PIC's ADC?

Blueteeth

 

[ikalogic]

I want to know the techniques,
How can we make Dual supply from Single supply???

I mean i have Regulated 5 Volts coming from LM7805 and i want to convert these voltages into +9 * 0 * -9...

Infact i need this supply for OPAMPS... as we know our common OPAMP UA741 and TL072 works on Dual power supply... And i want to connect OPAMP output to PIC ADC...

I have seen Nigels analog board but he use IC and that IC is not available in our local market...

Thanks...

hello ayne.. there are many opamps that do not need dual power supply.. example the LM358, which i would say is fair the 741 is really old and maybe the worst op-amp available by those days! (still i know it used to teach in universities in my country.. )

 

[audioguru]

I have made thousands of circuits with the TL072 dual opamp and none of them used a dual polarity supply. Just bias the opamp input near half of the supply voltage and it works fine.

The old LM358 and its quad opamp sister the old LM324 are worse than the old, old 741 opamp. They have a bandwidth to only 6kHz at half their max output level (less at max output level) and have crossover distortion.

People who cannot buy common ordinary electronic parts "in their local market" should do gardening instead of electronics.

 

[Blueteeth]

People who cannot buy common ordinary electronic parts "in their local market" should do gardening instead of electronics.

Either that or 'make do' with what they have. If we all had access to any parts we needed, then all the inovations in the electronics world would be made by electornics manufacturers. It's beneficial to be limited by parts, it makes one think, and be resourceful and adapt to the problem. Sure, maybe for professional products its not ideal, but for hobbyists, and prototypes, you just have to work out a substitute circuit...unless you always take the easy route?

Blueteeth

 

[Hero999]

Why not build a DC supply in the first place?

Please post a schematic of your power supply, it's probably fairly easy to make it into a bipolat supply so long as it isn't based on a DC adaptor.

 

[ericgibbs]

hi ayne,
You say, i have Regulated 5 Volts coming from LM7805

Do you have access to the input side of the 7805, if so, measure the voltage, if you have around +12Vin,
it should be possible to connect a 78L09 to give you +9V.

Buy a low cost, 12Vdc 250mA, plug mounted psu and use a 79L09 to give you -9V

Lets know what you measure to the input of the 7805.

Eric

 

[audioguru]

I have always had access to new ICs, bought them, and learned all about them by using them.

The 7660 is not new and is made by many IC manufacturers. Why isn't it available over there?

 

[ericgibbs]

hi audioguru,

Working in the UK, I have no problem getting components, but when I go overseas to a 'developing' country,
getting the simplest component can be a nightmare.

A lot of the components and pcb's for PC's, are pieces that went obsolete in the UK years ago.
I suspect these countries are dumping grounds for old stock the 'stockists' can't shift in 'developed' countries.

Eric

 

[Thunderchild]

People who cannot buy common ordinary electronic parts "in their local market" should do gardening instead of electronics.

well conside audioguru that it took me 6 months to get a simple power amplifier IC here in Italy the TDA2002 what was I supposed to do use 1000 TL082's in paralel to obtain the same power ? there are countries where DIY is either not looked upon and often purposely discouraged by lack of availability and cooperation from suppliers and dealers, I mean I can take up skiing in any country can't I ? but if I have to wait a year before I get a pair of skiis I order this winter most likely by next winter I will have given up on the idea.

I tried to make a theremin and could not even get one of the chips ridicolous no dealer in my range even had it on thier supplyers list of available parts

 

[audioguru]

well consider audioguru that it took me 6 months to get a simple power amplifier IC here in Italy the TDA2002

Sure, it is obsolete and has been replaced by the much better TDA2003.
There are over 100 similar power amplifier ICs for cars from ST Micro and Philips.
www.farnell.com in Italy has lots of them.

 

[Thunderchild]

hm yea but all I can to is toter down to my local tv repairer and ask him to order me stuff. now he has like 10 suppliers and yes start to wounder why does one need ten suppliers for the same stuff ? I have no access to internet buying as I have no debit/credit card and frankly I find absurd that I can hardly order stuff. I phone a man up he goes and looks on his computer and tells me he can't get me IC "x" or any replacement I mean are we joking. do you know how many projects I have just tossed to the wind cause I knew I would never get the parts ?

 

[audioguru]

I make my order for electronic parts online for a reasonable price one evening and they are delivered to me the next morning. No tottering anywhere.

 

[Ayne]

That IC(Nigel use) is available here on one shop but it is enough coastly... Therefore i am asking some other techniques using low coast components..

People who cannot buy common ordinary electronic parts "in their local market" should do gardening instead of electronics.

Haha

 

[Nigel Goodwin]

That IC(Nigel use) is available here on one shop but it is enough coastly... Therefore i am asking some other techniques using low coast components..

But how would we know what components are cheap other there?, the 7660 is a common cheap IC.

Easiest solution, use two 9V batteries!.

 

[audioguru]

The ICL7660 IC is only $.80US at Digikey. They have thousands of them.

 

[Thunderchild]

well lucky you but in southern Italy even professionals can wait months for parts

 

[audioguru]

I didn't know that Italy is a 3rd world country.
Don't you have electricity and running water yet?