Okay, I’ll get the ball rolling.
I wanted see if I could get some suggestions on powering my current project. It’s a small PIC based timer for controlling an RC servo motor for parachute deployment. I want to give people the option to power the timer from as many possible power sources as possible. The circuit itself will probably draw 20mA at most, but since people will supply their own RC servo motor they could potentially draw up to 1 Amp, though 100-300mA would be more common for the small servos.
The timer can run from 2 to 5.5V, but the standard servo requires 4.8 - 6V. I would like to be able to power the whole thing from anywhere between 6 and 9V (perhaps 12V?). That allows people to use a heavy but simple 9V battery or a lighter 6V battery (such as 2 x 3V CR123As) or a pair of small and very lightweight LiPos at 7.4V. etc.
I normally use a 7805 regulator with a 9V battery (as with my previous project http://www.aircommandrockets.com/flight_computer_V1_6.htm
) or optionally 6V battery with a simple (but inefficient) power diode to drop the voltage. I couldn't use a 7805 due to its drop out voltage.
My main question is this: Is there a surface mount regulator that I could use over the input voltage range (6-9V) to give me something in the 4.8-5.5V range with the 1amp capability? Ideally the target voltage would be 5V. I have tried looking at LDO regulators, but I don’t have any experience with them, or what their limitations are at higher currents, or whether they are even right for the job.
Should I leave the voltage regulator off and let people make up their own power supplies? Though I want to make it as simple for the user as possible.
If it's not possible to do it with one solution should I let people order different versions for different voltages?
What other considerations should I take into account in the power supply such as filtering, polarity reverse protection?
What voltage do common rocket electronics normally run at?
Any other suggestions would be most welcome.The project:
It is a simple delay timer that activates a single RC servo motor to be used for parachute deployment on water rockets. The timer allows you to configure the start and end servo motor positions (stores them in the EEPROM internally) and you can select a delay as needed.
The main motivation is to keep it as inexpensive as possible as many water rocketeers are really on shoe string budgets. Small size and weight are also important, not just for flying on rockets, but also shipping through the post. It will also have a small footprint.
The system just self arms 10 seconds after power-on and detects launch to start the timer. I’m also giving the user a number of options for triggering the timer either through a built in G-switch, or external make or break contacts.
You can select the delay in 1 second increments up to 13 seconds, where a 0 delay can be used when the trigger comes from apogee detecting sensors such as the uMAD, barometric sensors or other flight computers. The 0 delay can also be used with burnout detecting sensors when the timer is used to activate a staging mechanism in multi-stage water rockets.