Recently, I have a project that needs to heat up a metal filament with a single pulse voltage. I built a circuit with 555 timer and transistors to heat up the metal filament(0.2 ohm). The circuit diagram is as below:
The circuit works pretty fine when R1C1=3s; 12V with 1.1A going through the load. However, when the time begins decreasing to 0.01s, the current reads from the output voltage source is very low (300 mA at 20V) and could not heat up the filament at all.
Normally, when directly connecting to voltage supply sources, the filament would light up at 2V with 1.5A. I wonder the way to light up the filament in such low pulse second. Could anyone help me with this? how to design?
【Update】 Thanks for comments. I forgot to put common ground. The D1 and R2, R3 is for trigger purposes. I click a button to trigger that circuit, but sometimes trigger time would longer than pulse time. So I put those components there.
I tried to build this circuit with one BJT before, but it encountered the same problem. It worked pretty well ~3s but it could not light up the filament in just~ms. That's why I tried to put another BJT to increase current(maybe it's a bad idea).
【Update】 Thanks for answer. Right now the filament could light up via the circuit below.
Still, there are some tiny detailed problems I encountered. First, the light intensity which comes out from the tungsten filament is not always the same. At mono-pulse 20 ms mode, it originally could not light up at 12V. But after pulse it again and again(small time gap(~1s) between each pulse), it becomes lighter and lighter until saturation. But after waiting a longer time gap, it returned back to its initial state which is darker or even could not light up. Though pulsing two to three pulse voltage(20 ms), it could finally light up again with saturation intensity. I am not sure why this happened. Maybe some parasitic inductor? Could anyone comment on this problem?