How to calculate resistor size for lasers in parallel - for dummies
I have four laser modules taken from laser pointers. Normally each module runs off of three hearing aid batteries in series, 1.5 volts per battery 4.5 volts total. I want to run all four laser modules off of two D size batteries which are 1.5 volts each 3 volts total in series.The problem is they will not light up when connected to the two D size batteries in series ? When I use a power supply they will light up even at only 1.5 volts ( although dim ) up to 5.5 volts,after that they become permanently dim, with the brightest at 3 volts. It seems like I have to limit the amps not necessarily the volts. Each module has its own resistor - the # on it is 680. When I measure the resistance it shows 68 ohms. What do I need to do to get this to work ? There must be some way to simply figure this out.... By the way I have about 40 more laser modules and I might like to use them all at once to make say..... an unquestionably visible turn signal bulb for my truck or maybe a very illuminating flood light for my backyard .... If I can figure this out the possibilities are endless !