March 20, 2010
Guten tag LMR,
Calculon is going to build this ciruit, but he wonders if his fellow LMR can comment on it before he starts. He's tested each component, but hasn't put them all together yet. Calculon's multimeter just blew a fuse, so he can't really measure the output at the moment. He has a wicked cool motor controller and he doesn't want to accidentally convert it to smoke. Here's the circuit:
M is a serial dual h-bridge powering 2x 2v 9amp gearmotors. The controller has an onboard regulator to power the ic. Not shown: 2 serial lines between M and IC.
Also, LED symbols are actually these guys and are drawing between 90 and 200 Ma each. Each runs to ground, but calculon only shows the digital inputs in his schematic.
Calculon wants to use 2 7805s in order to cut down on the heat.
1: The numbers: 300 mah to the sensors. Voltage drop is 7v. = 2.1 Watts burned off. At 50C/Watt heat dissapation, that means the 7805 should be 100 degrees above ambient?
2: Can one 7805 safely handle double that amount? Is 2 a bad idea?
3: Also, will the voltage drop be 7, or will it be less than that, due to the motor controller?
4:Should the ICs ground line Y connect back to M, or should it run down to 0v?