Questions on powering the EL Sequencer with external power

Development Boards Other Microcontrollers
1

In the power section of the EL Sequencer Hookup Guide https://learn.sparkfun.com/tutorials/el … 1567448645 it says “Using an external power supply with the 3V inverter will require closing SJ1.” From this I gather that I can power both the board and the wires using the inverter power supply. Which is perfect for what I have in mind.

Two questions:

  1. Is that true?

  2. The guide specifically mentions the 3v inverter. But I need the 12v inverter for the wires I have. Do I short SJ1 for the 12v inverter? Will that work to power both the board and the wires? (OK, three questions…)

2

Hi toc!

“Using an external power supply with the 3V inverter will require closing SJ1.” From this I gather that I can power both the board and the wires using the inverter power supply.

  1. Is that true?

It’s true, but only in the following case:

  • - You're connecting a single cell (3.7-4.2 volts max) Lipo battery to the Batt In connector.
  • - You're using our 3.3 volt inverter connected to the DC out connector.

    • What SJ1 does is bypass the voltage regulator that reduces the voltage on the Batt in socket and ouputs it on the DC out socket. When you run the board directly from a lipo battery and pass that through the regulator, the voltage drop is enough to make the inverter not work well. (the regulator will drop the input voltage by roughly 1.3 volts) By closing the jumper, you bypass the regulator and feed raw battery voltage into the inverter. A freshly charged battery will output about 4.2 volts and that is technically a bit more than the inverter is rated for, but the inverter copes with a slight over voltage better than it does with a slight under voltage.

    1. The guide specifically mentions the 3v inverter. But I need the 12v inverter for the wires I have. Do I short SJ1 for the 12v inverter? Will that work to power both the board and the wires? (OK, three questions…)

    If you’re using the 12 volt inverter and you have a 12 volt power supply connected to Batt in, you will want to close SJ1. My suggestion is to close SJ1, connect 12 volts to Batt in and connect the DC input on the inverter to DC out. That will provide 12 volts to the inverter and the board will regulate the 12 volt power input down to 3.3 volts for the ATmega chip that’s running your code.

    3

    Thanks! That sounds exactly like what I needed to know!