The following schematic snippet shows a 555 output driving a pair of transistors (are they still a Darlington pair even if different??) - the load connected to the collector of the TIP3055 is a rocket ignitor. This and the leads attached to it have a combined resistance minimum about 1 Ohm.
I do have a working version of this, it ignites rockets no problem... From memory the bias resistor on the BC547 is 50 Ohm (I can't recall) - at the time I chose this value, as a higher one seemed to not allow the TIP3055 to conduct fully (I think!)....
What I was after was an educated/calculated approach to how to calculate the best bias resistor here.
The aim is for the TIP3055 to switch fully on, and allow maximum current into the load. Of course the load disintegrates a fraction of a second after ignition....
Thanks in advance
Lee
I do have a working version of this, it ignites rockets no problem... From memory the bias resistor on the BC547 is 50 Ohm (I can't recall) - at the time I chose this value, as a higher one seemed to not allow the TIP3055 to conduct fully (I think!)....
What I was after was an educated/calculated approach to how to calculate the best bias resistor here.
The aim is for the TIP3055 to switch fully on, and allow maximum current into the load. Of course the load disintegrates a fraction of a second after ignition....
Thanks in advance
Lee
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