The stencil finally arrived! We will be reflow soldering tomorrow or Wednesday
Tested force sensing resistor. See schematic. Using R1 = 22 kOhms, we expected Vout to be roughly 2 V. But the observed value was 4.8 V. We think we are using the sensor incorrectly or we have a fautly or incorrect part. We may try 3D printing a pressure plate that fits exactly onto the active area of the force sensing resistor. - Spencer, Rohit
Wednesday March 21, 2018
Reflow soldered the board. There were issues with solder
bridges, but they were not too big of a problem. We just remelted
the solder and the bridges melted. See pictures.
The motor driver PCB is ready for reflow
Notice the solder bridges on the TQFP chip
Solder bridges melted - no more shorts
PCB with through hole components soldered
- Spencer, Rohit, Evan"Smoke Test": slowly ramping up the microcontorller power to 5V. Set the power supply current limit to 100 mA and monitor the current.
Smoke test passed. Drawing around 20 mA at 5 V (ATMEGA2560 is just running nothing, or whatever it had from the factory, plus current draw of the logic for the L298 motor driver). - Spencer