Currently I am doing a project on building an automatic bp monitor. For this I am using a 6 volt micro air pump which consumes 430 mA current and a 6volt solenoid valve which cosumes 60 mA current. I have to switch them both simultaneously. I used a 6F22 9 volt battery as a power supply and used BD135 NPN BJT as a switching device. The battery is 400mAh. The input voltage is 5 volt at the base. I used a 1k pot as a base resistance then I varied it to see the motor speed. But the pump runs at medium speed and when I switch the solenoid valve along with it the speed drops further. My questions are- 1. Is BD135 a good choice or should I switch to another NPN bjt? 2.If BD135 is ok,then what will be the suitable base resistances to drive both the pump and valve? 3. I used a 9volt battery rating 400mAh, is it ok? 4.Should I use TIP132?
A 6F22 9V battery (called PP3 in the UK) isn't up to powering motors, which the exception of some of the rechargable NiMH versions, 0.5A would defeat it.
You need something like a 6V battery pack from AA's or AAA's to get the current handling I think. Or maybe first try a NiMH 9V pack of reputable brand.