I have a component in a project that requires a voltage of -15v. I did several google searches and cannot wrap my head around how I would go about producing negative voltage. If anyone could suggest some circuits/components that would convert +5v to -15v that would be amazing. Thanks in advance!
-Sciortino
Negative voltage simply means is has less potential than the ground. If you do not have a specific constraint for where the ground should be, you can use two identical batteries like this : http://i.stack.imgur.com/M47w4.png
(forget the capacitors)
What would you like to use as a power supply ?
Wait for more replies, but I think you could get an isolated dc/dc boost converter to get +15v, then use the load sides positive as the negative and the load sides negative as the positive.
Not sure how well putting a boost converter's output in the ground path will work???...
I would suggest building a separate supply using a bell transformer, a bridge rectifier, a big filter cap, and negative linear regulator (7915, 78M15, I think), where the regulator's input comes from the negative output of the bridge, not the positive side. Then, as deathstar suggests, connect the positive side of the new supply to arduino circuit's ground, and the negative side (-15V) to the appliance requiring the -15 volts.
There are several ways to do it. Normally, I just build a bipolar power supply as shown in figure 7 or 8 [u]here[/u]. Or you can buy a bi-polar supply, or a supply with multiple outputs.
When I needed -12V for an op-amp in a car, I used something like [u]this[/u]. (That particular one needs more than 5V, and of course I don't know how much current you need.)
I think before we get into more options on how to make the negative supply, please tell us what you need it for (a link to a schematic, article etc.) that mentions it.
// Per.
The MC34063 can be wired up as an inverting switch mode regulator/converter.
http://www.nomad.ee/micros/mc34063a/
I entered:
5V In
-15V Out
50mA Out
50mV Ripple
20kHz Fmin
And got:
Ct=1588 pF
Ipk=485 mA
Rsc=0.619 Ohm
Lmin=327 uH
Co=357 uF
R1=1k R2=11k (15V)
It also alters the schematic to display it accurately depending on if your output is greater or less than Vin, or negative.
Note how high Ipk is when the output current is only 50mA. That is because not only are you stepping the voltage up, it is negative so it isn't just increasing it by 10V as it would if the output were merely positive 15V, it must actually change it by 20V as 5V - -15V = 20V, plus switch voltages and losses.
So as Zapro says, we need to know what this is for and how much power you need.
Sciortino:
I have a component in a project that requires a voltage of -15v. I did several google searches and cannot wrap my head around how I would go about producing negative voltage. If anyone could suggest some circuits/components that would convert +5v to -15v that would be amazing. Thanks in advance!-Sciortino
If its an opamp you probably ought to find a rail-to-rail one instead.
One vital missing piece of information is how much current you need to take from the -15V. The more current the more expensive is your solution.
Id just buy a dual voltage supply on digikey, they give +15, ground and -15 V, . +15 to +5 is easy with voltage regulator.
Everyone rushing around like headless chooks!
Think, people - XY problem!
Is Zapro the only one to pick up on this? We need the OP to explain how he knows the LCD display requires negative 15 volts in particular and it would help for him to post any further information he has beyond the HI-8010P-03 datasheet as well as a set of perfectly focussed photos of the module.
Paul,
As an ignorant Texan, I must ask "What's a 'chook'?"
As an aside, if we all don't just assume we already know everything there is to know and that we, alone, have the perfect solution, how are we going to help the OP turn his Arduino into a smoldering heap copper, epoxy, and fiberglass?
