I've tried putting 2 diodes together which should drop 1.4V in theory but in practice it was all over the place, anywhere between 4.5V and 3.0V depending on what the device was doing.
A simple Zener diode voltage regulator might do the trick. I punched the maximum values you mentioned into this online calculator and it appears a 14 Ohm resistor (so you'd use a 15R) along with the 3.6V Zener diode will cover it off nicely. A very cheap solution too.
First are you sure that the project needs exactly 3.6V? Maybe 3.3V is OK - but you've neglected to provide any hard information about this project like a link to tech-specs or a datasheet - please do so.
Quote from: fungus on Apr 27, 2013, 12:56 pmI've tried putting 2 diodes together which should drop 1.4V in theory but in practice it was all over the place, anywhere between 4.5V and 3.0V depending on what the device was doing.Wow, this device sure has variable current needs.
Before anyone can give you truly meaningful advice, we'd need to know a little more. Can you tell us:1) What the device is (link to spec sheet would be nice)?2) Voltage tolerance of the device?3) Current requirements of eh device?4) Any other hard facts that might be pertinent to your use of the device?
With the zener and a 15 ohm resistor you'd be burning off nearly a watt of power.
I'd strongly suggest the voltage regulator circuit (first one) that runaway pancake suggested. Use 4.3V-4.4V zener. The rest of the values look good but you could use any resistor from about 500 to 2K and the cap could be almost any value (10uF - 330uF, whatever).
The "voltage regulator" circuit. Instead of using a zener, assuming the 5V supply is regulated, you could use a divider to establish VB (the values chosen will effect IB.)
So, my suggestion (reply #2) is just a bridge too far then?