Hey everyone. I am currently working on an LFR with the Arduino mega.
Here's the issue. I have connected to the Arduino 5 ir sensors. Motor driver is spark fun monster moto shield. Total current draw of all components from the 5 volt pin is 128 mA.
The voltage regulator overheats too much. Measured the temp it was above 100C (disconnected after 100C as i was afraid something would melt)
I am using a 12 volt LiPo battery. Battery voltage is 12.37 V.
Is using a heatsink in this case advisable?
Would it be better to use a buck converter and supply the mega with less than 10 volts?
Not much better. You could spread the heat generated over 2 regulators (on-board + external) which would help somewhat, but still more than half the power would be wasted as heat. The regulators would still be dropping 7V out of 12V between them to output 5V, so the efficiently would be 42% and all power wasted turns to heat.
EDIT: Sorry, I misread your last post. Yes, using a buck converter to reduce 12V to 9V would increase the efficiency from 42% to maybe 50%.
A buck or voltage converter reducing 12V directly to 5V could be 85~90% efficient. You would set it to 5V output and power the Mega through its 5V pin.
In order to set them to 5V one needs to either set the pot so the output is 5V or cut the trace at the adj jumper pad and solder across the 5V jumper pads. I like to do the latter so the the pot can't be mis-adjusted and fry things.
Hi,
Can you post a circuit diagram showing how you would use the LM7805 with the Mega please?
Hand drawn and photographed circuit is perfectly acceptable.
You can use the LM7805 to provide 5V to the 5V pin of the Mega, BUT you will possibly need a heatsink on it and the appropriate bypass capacitors.
The heatsink is because it is a linear regulator like in the Mega that is over heating, and although the LM7805 may not get as hot, it still needs to dissipate the same amount of energy as the Mega regulator did.
Alright so here's what i plan to do now
Attach a buck/boost converter to the output of the battery and set it at 5Volts output
Plug in output from converter to mega's 5V pin
Attaching pic of buck/boost converter below
Any improvement i should make?
One more question. Is it ok to connect all grounds together? (seems like a stupid question now that i think of it)
So like battery, motor driver and arduino grounds connected together, though they operate at different voltages.
Not just OK, it is required. Ground is the common reference between the parts.
To be sure though, please post a schematic showing all of the parts and power supplies. Hand drawn, photographed and posted is fine if you don't have a CAD program. If you want to try CAD, here is a good start.
