micromouseonline
commented
4 years ago Driving the emitters direct from the battery without some kind of constant current source is risky because the battery voltage will fluctuate as the robot runs. Not only will the voltage decrease with state of charge but high power motors and high accelerations will make it sag significantly over shorter intervals.
It is not clear how to perform reliable compensation of sensor readings for fluctuations in supply voltage so a regulated emitter supply is used.
The regulator on the (genuine) Arduino Nano is an LM1117 and is rated as good for 800mA. Anticipated emitter currents are much lower and are unlikely to exceed 200mA for short periods. Prolonged currents in excess of, say, 150mA may well cause heating. It remains to be seen if that is problematic but pulsing of the emitters will ensure that the average current is kept modest.
The LM1117 is a good regulator and is capable of better than 50dB ripple even at its maximum 800mA load.
gbulmer
Phase: Revision 2 Artefacts impacted: ukmarsbot-brd-20190804A.pdf and underlying UKMARSBot PCB ECAD
Suggestion: A sensor board using high-power LEDs could half its power needs by using LEDs in series running at 7V+ (V_BATT). It would also slightly increase battery life. The extra voltage headroom might help sensor boards which would benefit from their own regulators.
Further, the sensor board currently draws about (SWAG) 130mA from the Arduino regulator. That's about 4x, or more, the ATmega's requirements. Taking demand off that regulator would help keep it cooler and maybe reduce electrical noise for analogue signals.
Using V-BATT for emitters may be helped because of the BATTERY_VOLTS monitor on A7.
Using V-BATT on a sensor board would be an option, and not a necessity. Hence there is no built in assumption in this issue that the Line sensor, or Wall sensor, needs to be re-engineered to use it.