[OpenTRV-dev] H-bridge transistor selection

[Stuart Poulton]

On 16/05/13 11:32, Mike Stirling wrote:
> Interesting. The poor performing transistors do so because he is 
> running them far too hard, although he does acknowledge this. He is 
> also running out of gain at the lower voltages, and would get an 
> improvement there by reducing the value of the 1k base resistor. This 
> is evidenced by the reduction in voltage drop with increasing supply 
> voltage. The important figures in the datasheet are Ic from the 
> absolute max ratings, which needs to be well above the expected stall 
> current of the motor, Vce-sat, which should be small, and the worst 
> case hFE (large signal current gain), which should be high enough to 
> allow for an acceptably low base current during motor stall 
> conditions. Mike 

Mike,

Coming up with a nice H-Bridge for battery operation would be great, esp 
if it could be driven with a low pin count from a uP.

I did measure the stall current of my dissected TRV head,

2 - Motor run current (no load)  13-15mA
3 - Motor Stall current - 95-100mA

Cheers

Stuart