This is an old revision of the document!
MFCitizen @Brussels
Michka Mélo, September 13th-14th, 2017
Abstract
Tests with resistor-based voltage divider
- FoAM's power supply does not go below 2.8 V of voltage.
- In order to control the voltage to a lower threshold, I built a resistor-based voltage divider.
- First version of the resistor-based voltage divider was made of a 100 ohms and a 10 ohms resistors in series. It worked but, smelled funny. After few runs, the 100 ohms had turned a nasty shade of black. It seems that the amount of current flowing in the resistor was too important because the resistor value was too low.
- The second version of the resistor-based voltage divider was made of a 2.2 kohms and 1 kohms resistors in series. No weird smells, it worked.
- However, I kept having funny results. I tested many of the components, and finally concluded with a test without the voltage divider that it might be perturbing the correct working of the circuit.
- I will therefore not present here the hectic results of these first tests.
Tests directly powered by the power supply
Test #1 - 1381E only
- When powering the 1381E voltage detector directly with the power supply (power supply + pin on 1381E pin 2, power supply - pin on 1381E pin 3, we obtain a 2.8V voltage on its output pin (pin 1), which is the same value as the one measured between the + and - pins of the power supply.
Test #2 - 1381E powering BBC microbit directly
- When connecting the BBC microbit 3V pin to the output pin of the 1381E, the BBC microbit does not light up (the GND pin of the BBC microbit The measured voltage
Test #3 - 1381E controlling 2N3904, which powers BBC microbit
Test #4 - Power supply feeding 1F supercap, powering the circuit
Test #5 - Power supply feeding 3F supercap, powering the circuit
Test #6 - Power supply feeding 10F supercap, powering the circuit
Explain why the second 2N3904 does not seem to light up. Tell the values of voltage drops
Test #7 - Higher power supply voltage
1381E threshold characterization
Future work
* Try out with higher