Turns out that these use basically the same driver as the more expensive ones that use a 1 watt pump diode. So, I edited the information I gave you earlier because it was wrong. These fastech modules use a 500 mW pump diode and if you don't have a bench power supply that can read the voltage and current you are using, you can use a fully charged Li-ion battery and measure the current going into the module with a DMM and adjust the pot so it doesn't draw more than 500 mW. My mistake.