Originally Posted by Dr.EM

If you are using the light detector to switch the flasher circuit, surely a MOSFET would be the best choice? Use a general purpose 2N7000 device, with an RDS-ON of 5 ohms, the voltage drop would be negligable. I think that's best, or does it need to be a P-channel? Similar P-channel devices are avialabe anyhow at a slightly higher cost. If you still want to use a BJT, which should perform fine providing the supply is high enough, use the 3906 for PNP, or 3904 for NPN, cheap and reliable

Thanks Dr.Em, I think I'll try joining my light sensitive switch circuit to my 555 timer circuit with a transistor and see what burns, glows, or blows. I'll use big resistors first and lower them gradually.

I've recently read that when deciding on components first decide what you want it to do, then decide what specifications are important.

Obviously with a transistor voltage, current and power handling are important. So I think I'll play a bit.