Hi all,
I have an H bridge circuit here that refuses to work. This is not powering a motor. Its for a 6V latching solenoid, with resistance of 2.5 ohms. It will happily energise at 600mA. However using this circuit, I can hear a faint click from the solenoid, so it is trying to energise it, but failing. I've measured collector emitter voltage on Q6 and its sitting at 0.5V, which tells me it's not saturated enough to drive 1A, but even if I drop R10 down to below 50 ohms, its still not enough.
I thought I'd done the calculations correctly for voltage drop through EB of Q6, CE of Q1, and BE of Q3. I've calculated for a 1A collector current at Q6 with a gain of 10 to be safe, so I'll need around 80-100mA through Q1 to give Q6 enough oomph.
Inputs are at R8 and R9. For the moment I'm touching them directly to the positive 6V rail to turn on Q1 and Q4, though NOT together. Just one at a time.
Am I missing something obvious here?
Thanks
Neal
I have an H bridge circuit here that refuses to work. This is not powering a motor. Its for a 6V latching solenoid, with resistance of 2.5 ohms. It will happily energise at 600mA. However using this circuit, I can hear a faint click from the solenoid, so it is trying to energise it, but failing. I've measured collector emitter voltage on Q6 and its sitting at 0.5V, which tells me it's not saturated enough to drive 1A, but even if I drop R10 down to below 50 ohms, its still not enough.
I thought I'd done the calculations correctly for voltage drop through EB of Q6, CE of Q1, and BE of Q3. I've calculated for a 1A collector current at Q6 with a gain of 10 to be safe, so I'll need around 80-100mA through Q1 to give Q6 enough oomph.
Inputs are at R8 and R9. For the moment I'm touching them directly to the positive 6V rail to turn on Q1 and Q4, though NOT together. Just one at a time.
Am I missing something obvious here?
Thanks
Neal