KAW RF - Adding 2x 100nF caps to HV circuit

Based on Mike Tranchemontagne's advice, I had previously added a 100nF to the High Voltage circuit of the KAW in order to boost the current to supply the RF circuit hack. This gave the results seen in the previous post.

 

The v_in was stuck at about 2.4V drawing about 56mA never reaching a higher voltage in order to activate the 3.3v regulator.  In order to see more energy and perhaps climb over this 2.4V I added another 100nF capacitor in parallel. In total this is 670nF (470nF + 100 nF + 100nF) which is a 43% increase in energy storage capacitance!

 

Start up the oscilloscope, and plug in the KAW! It's not the smoothest but after a few seconds, the circuit does achieve its goal to power the moteino microprocessor!

1) 0.0 to 12.5 (12.5 seconds) output is about 2.3 V. The KAW screen is completely dark during this time not displaying anything.
2) 12.5 to 21.3 (8.8 seconds) output is about 3.3 V. You can see the 13V9 line start to increase, and this is not causing a proportional climb in the v_in. The KAW screen is now showing the correct voltage on screen.
3) After 22 seconds the output finally reaches about 5V for steady operation on both the KAW and the moteino.

KAW RF - Issues with initialization voltages

I’m still having issues properly loading the Moteino using the KAW on startup. I’ve been fooling with the code yesterday to once again confirm that the code will execute fine if enough power is in the capacitor but never load if capacitor never reaches a voltage higher than the required v_min of the moteino 3.3V voltage regulator. Since I now have an oscilloscope, I decided to give it a go and investigate how much voltage I am feeding it when I plug in the KAW.


Yellow Channel = 13V9 red wire to KAW

Blue Channel = vin output power circuit

The first test is to connect the KAW and no moteino load after the charging capacitor. The screenshot below shows the output rising to about 5.3V at 1.1 sec and settling to 6V in 1.7 sec. The 13V9 line also looks to be taking its time to settle at its voltage. Also note that I've added an extra 100nF (250V) to the 470nF capacitor of the KAW High Voltage circuit.

With the Moteino connected you can see the waveforms now smaller in magnitude, never reaching the voltage seen before. The output after a few minutes will settle at about 2.4V, never reaching the v_min to power up the moteino.

The output is also extremely noisy! I think I'll start by studying the power circuit drawn from the KAW. The RC values might need some adjustments to decrease the time to charge the capacitor, I'll try reducing the resistor to see if it yields a positive outcome.