Hey!
I'm motorizing a small truck (1:87) and I need to make a H-bridge of some sort that can be powered with just 2.4V (two NiMH cells). It will be controlled by an AVR micro controller, which runs on 5V from a boost converter that can't supply the motor. I haven't actually measured what current the motor takes but I guess it would be about 200mA running freely and perhaps 1A holding it still.
Now, space is sort of an issue and since I want all sorts of other functions, I think I'll use SMT. I really just have about 1x2 inches or so, perhaps two layers with pin headers in between if the components aren't that high.
I've looked at some MOSFETs and the only one I found that might work and was available was the IRF7105. I've looked at using "normal" transistors but found that the SOT-23 package would get to hot (generalization), since the Rthj-amb≈500°C/W. I could probably cram in some SOT-223 (eg BCP55) but I'd prefer something smaller. And then I would need some schottky diodes as well...
So, I'm open to suggestions, MOSFET/BJT, SMT/through-hole, low-voltage/more NiMH cells, cooling?
Thanks!
I'm motorizing a small truck (1:87) and I need to make a H-bridge of some sort that can be powered with just 2.4V (two NiMH cells). It will be controlled by an AVR micro controller, which runs on 5V from a boost converter that can't supply the motor. I haven't actually measured what current the motor takes but I guess it would be about 200mA running freely and perhaps 1A holding it still.
Now, space is sort of an issue and since I want all sorts of other functions, I think I'll use SMT. I really just have about 1x2 inches or so, perhaps two layers with pin headers in between if the components aren't that high.
I've looked at some MOSFETs and the only one I found that might work and was available was the IRF7105. I've looked at using "normal" transistors but found that the SOT-23 package would get to hot (generalization), since the Rthj-amb≈500°C/W. I could probably cram in some SOT-223 (eg BCP55) but I'd prefer something smaller. And then I would need some schottky diodes as well...
So, I'm open to suggestions, MOSFET/BJT, SMT/through-hole, low-voltage/more NiMH cells, cooling?
Thanks!