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Hello There!
Now, heres my first Instructable and Ill show you, how to make a small Voltage Inverter (I mean, getting a NEGATIVE Voltage out of a POSITIVE) on you Bredboard.

Some Amplifying circuits need negative voltage to work good. This circuit schould deliver enough current to power a small OpAmp or so.

Step 1: Part List


Now, youll' need some Parts you can easily from you local electronics store.

-1x Bredboard (To mount everything on, you could even use a small Stripboard to solder everthing on)
-1x NE555 (Tiny Timer Chip, the Heart of the Circuit)
-Capacitors: -1x 25 Volt, 47 - 220µF (For Testing, Get more than One ;))
                       -1x 16 Volt (or Higher), 0.1 - 1µF (Same Here)
                       -1x 25 Volt (or Higher) 470 - 2200µF
Resistors: -3x 1.5kOhm ( 1k will work,too)
                    -1x 100kOhm (With this one you could Mess around, so you could use anything between 1k - 820k, Its up to you!)
-2x 1N4001 Diode (You can use nearly every kind of Diode, but prevent using Zener Diodes. They wont work.)
- 9V Battery or other Powersupply (If youre' using a Wallwart, make sure you put some Ripple-filter caps on the powerlines)
Finally, Some LEDs with the color of your choice.2 - 3 or so.

Step 2: Adding the 555Timer Chip

Just Follow the steps to get your Chip working.

Photo 1: The Schematics of the Timercircuit.

Photo 2: Put your 555 on the Board just like this.

Photo 3: Connect the supply pins to V+ and GND. Mouseover the Photo to see which pin is the V+,GND and RESET.

Photo 4: Add a small bridge from Pin 6 to Pin 2.

Photo 5: Add the 1,5k and the 100k Ohm resistors.

Photo 6: Add a Capacitor with something around 0.47µF.

Photo 7: Beware of the Negative and the Positive connections of the cap!

Photo 8: Same as the cap, the LED has a positive and a negative connection,too.
The shorter leg is the (-) negative connection.

Photo 9: Add a 1.5k Ohm resistior and Plug your LED in.

Now, Connect Power. Your LED should blink. If it does, go to Step 3.
If it doesnt, check all connections, and make sure everything is right.

Step 3: Add Diodes and Capacitors

We want this Circuit to Invert our voltage, so well have to add a few more parts.
Photo 1: The whole circuit.

Photo 2: Every electrolytic capacitor has a + and a - connection.

Photo 3: Connect the positive side of your cap with the Output Pin (Pin 3) of your 555.

Photo 4: Same as the Cap, your diodes have got an Anode (+) and a Cathode (-).

Photo 5: Connect your diode like this.From the negative pin of the cap to the side of the diode without the stripe. The  side with the stripe goes to GND.

Photo 6: Put your second diode in like this.The striped side goes to the negative connection of the capacitor.Just use a free place for the second pin of the diode.

Photo 7: Big Cap!

Photo 8: Place this with the positive lead to the GND line of your bredboard and the negative lead to the non-striped side of you second diode. Do not connect wrong.This could damage your 555 or you cap!

Photo 9: The finished circuit.

Step 4: Testing


I hope you know, you couldnt drive more than some milliamps of this circuit.
And there are some switching losses, so you wont get -9V if you put +9V onto it.
Thats because of the Diode-Drop Voltage, and because this circuit isnt' very efficient.

These Photos show the performance of the circuit.
I got just abaout 7,4 Volts without any load, and around 6.5 Volts with a LED as load.

I hope you like it!
Does this produce AC or DC current
<p>I believe inverters produce AC voltage (DC to AC)</p>
<p>This circuit is <em>literally</em> a voltage inverter, i.e. it 'flips' some voltage above ground to some voltage below zero. An inverter of the kind you mention (which produces AC from DC) is way more complex and expensive, and a different circuit altogether.</p><p>The circuit shown here only deals with DC, does not mess at all with AC.</p>
The final product
Thanks for the awesome and useful little project I built this and it works great. Running it on a +12V power supply gets me about -10.62V. I started with it in the test phase on my breadboard and then from there made it a more permanent solution soldering it on a pcb.<br><br> I'd really like to be able to make it adjustable so I could get exactly what I needed for each project I use it for. I'm trying to find the best way to do that. If you have any suggestions, I would love to hear back from you. Thanks again!
<p>will this work for a 12V supply?</p><p>Please answer as quickly as possible.</p>
<p>yes it will</p>
<p>thankx</p>
<p>It was easy and I made it for my school project. I also got a first price for this. Thank you</p>
you said Bredboard
I just posted this on the arduino forum to drive LCD contrast, course its not my idea, and I would have never thought of it, but durn if you were a couple days earlier it would have saved me a boatload of googling

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