Hi there,
I'm using RF433 modules to transmit data around my house and I want to boost the range by upping the voltage. The transmitters now operate at the voltage supplied by the arduino's (3.3v or 5v).
I have a 12v power supply that delivers around 12.6v when I measure the voltage with my multimeter. When I connect it to the RF transmitter it won't send, so I figured that it might be because the transmitter can't handle more than 12v. Could that be the case?
When I try with a 9v battery the transmitter does send and it indeed has quite more range.
What should I do? Get a 12v voltage regulator? Or should I aim lower than 12v? Can I use a voltage divider circuit with resistors? Can you help with that?
Thanks a lot
Look at the data sheet for the transmitter. It will have an operating voltage range. Use a voltage regulator for the top of that range. But do not use "Absolute Maximum Ratings". Those are not for normal operation, they are absolute DO NOT EXCEED ratings.
Did you measure your power supply unloaded? If that is the case, it might well sag a bit when you make it work for a living. I see no reason why you shouldn't use 12 volts on your modules, if that is what they're rated for. I'd still go with a regulator though... I like to know what I have. The drop-out voltage of a normal regulator will probably prevent you from getting the entire 12V from your power supply, but you can certainly get the majority of it.
Allright guys, thanks for the advice. I'll get a few of those regulators and test it out! I also like to know what I get. 
In the meanwhile I used this tutorial to find out that I could use resistors 470 and 33k ohm to divide the voltage. It is now working on 10.5v
https://learn.sparkfun.com/tutorials/voltage-dividers
Definitely not a voltage divider unless your modules don't draw much power. Try a adjustable voltage regulator such as a LM317.
http://www.digikey.com/product-search/en/integrated-circuits-ics/pmic-voltage-regulators-linear-ldo/2556290
Can sort/filter by voltage and other key specs - whether or not you buy from digikey (I recommend them highly), they've got a great catalog for discovering parts.
Also - instead of jacking up the voltage... what kind of receivers are you using?
Are you using the green ones with the single SOIC-8 package in the corner (an opamp) and no crystal? Those are superregenerative receivers - and they're kinda crappy. The thin yellow ones marked RXB12 with the crystal and SOIC-14 package (a SYN470) are superhet receivers, and I get markedly better range with them. They're a buck and change each shipped on ebay.
just put one or two diodes (e.g. 1n4001) between your voltage supply/battery and your circuit.
each diode will lower the voltage by 0.7 volts.
do NOT use a resistor, because the voltage drop is too dependent on the load.
forget about voltage regulators, as these require a minimum of 1.5 to 2.5 volts between V(in) and V(out).
arduinoaleman, have you heard about LDO voltage regulators? We have linked to these. Please pay attention to previous posts.
arduinoaleman:
just put one or two diodes (e.g. 1n4001) between your voltage supply/battery and your circuit.
each diode will lower the voltage by 0.7 volts.
Great info, thanks for posting this. I'm getting on of thhose 12v regulators to be sure but I really appreciate the info. I'm sure this knowledge will come in handy soon.
Different diodes will have different voltage drops. Do not use a Schottky diode to drop voltage!