Hello I am working on my project and discovered the wonders of the Attiny85, and all is working so far but i have run into one dilemma. I have searched all over and haven't quite found what i was looking for(sorry if there is a forum out there like this). In my project i will be running a small pump(I have hooked it up to my Arduino Uno and it worked perfectly) but i want to down size it to the Attiny and the question is can i use a simple voltage divider to power the Attiny? I would like to use a a 1k resistor and a 2.2k resistor to cut the 12v down to approx 3.75 volts. I did not know if i cut down the voltage what that would do to the current and if i would still be able to drive a TIP120 transistor from this or not. I do not really want to use a voltage regulator as i need the space. Let me know if you think this would work or if you have any other suggestions. Thank You
speedjayg, There must be hundreds of questions about this on the forum, all the experts say not to use voltage dividers for power. The change in current draw of normal operation will vary the voltage. E-Bay has very cheap regulators, search for "dc dc step down converter", $1.50 on up from China, about three times that for ones shipped from the US. I use them exclusively now, linear regulators are simpler but waste more power as heat. TomJ
Tumbleweed: There must be hundreds of questions about this on the forum, all the experts say not to use voltage dividers for power. The change in current draw of normal operation will vary the voltage.
You can use a voltage divider to power a device but you can't just put two resistors on a breadboard then connect whatever you like to the middle of it. You need to know the exact current draw of the device before you pick the resistors.
Plus it's horribly inefficient - 80-90% of the power will be wasted as heat.
If the current requirement is low enough, you can use a resistor + zener diode (like a voltage divider, but the lower resistor is replaced by a zener diode). But why not use a small 5V regulator? You can get them in TO92 (through hole) and SOT-23 (SMD) packages.
I do not really want to use a voltage regulator as i need the space.
You can get small voltage regulators.
Usually they’re big because they need to dissipate heat but if your current requirement is small (eg. An ATtiny) then you can use a small one.
Please, please use a voltage regulator... if you are trying to save board space, there are SOT23 packaged LM7805s. It really not that complicated and will save you a lot hassle.