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leongch
Joined: 22 Dec 2005
Posts: 40
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 22 Mar 2006 20:01 How to get negative voltage supply from +DC Voltage supply |
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hi, i only got DC adapter and 78L12 and 78L05 ... how could i get a -12V and -5V from the components above? Any other circuit recommended which provide -12V and -5V from positive DC voltage source? I need it in urgent... Project due soon
Thanks a lots
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buenos
Joined: 24 Oct 2005
Posts: 657
Helped: 15
Location: UK
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22 Mar 2006 21:07 How to get negative voltage supply from +DC Voltage supply |
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| if you want a (+) and a (-) supply in the same time, from a single positive DC adapter, then you need a switching regulator inverter, or a charge pump to get the negative voltage.
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BeeBop
Joined: 19 Feb 2006
Posts: 161
Helped: 15
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23 Mar 2006 4:13 Re: How to get negative voltage supply from +DC Voltage supp |
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Hello,
Depending on what you are doing with it, you may be able to just invert your power supply. What I mean by this is using the + terminal as a ground, and the - side of your supply as your negative voltage, since voltage is relative. In many cases, you could build a supply with one 78xx regulator circuit in parallel with another, to give a + & - supply. Hope this makes sense, but if you have any questions, just ask, and I'll help.
Regards,
Robert
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23 Mar 2006 4:13 Ads |
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IanP
Joined: 05 Oct 2004
Posts: 6490
Helped: 1542
Location: West Coast
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23 Mar 2006 4:33 Re: How to get negative voltage supply from +DC Voltage supp |
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To generate low-current negative voltages you can use 555 timer IC ..
Take a look at the circuit below ..
If supplied from 12V, and without 5.1V zener diode it will generate ≈ -11V (always 1V less than positive supply) ..
With 5.1 zener diode, it will supply ≈ -5.1V ..
Regards,
IanP
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