Why did you request that I change the circuit to allow two signals so that direction could be separately energized, and then use a single signal with an inverter?
My first circuit would do what you want without the inverter.
Why did you request that I change the circuit to allow two signals so that direction could be separately energized, and then use a single signal with an inverter?
My first circuit would do what you want without the inverter.
Why did you request that I change the circuit to allow two signals so that direction could be separately energized, and then use a single signal with an inverter?
My first circuit would do what you want without the inverter.
Both M1 and M2 are N-channel, the same as in your second circuit. When powering up, M2 conducts once, then switches over to M2 which stays in conductive mode (frequency is about 1Hz). Source and drain are correctly wired, I checked and rechecked and..
I have no clue at the moment; your circuit is very logical, yet here it does not work.
I put a scope on it: M2 stays conductive, the drain never goes high, the gate does alternate high and low (and M2 gets hot as hell).
I don't understand this..
I put a scope on it: M2 stays conductive, the drain never goes high, the gate does alternate high and low (and M2 gets hot as hell).
I don't understand this..
To which transistor are you referring to when you say M2?
Which gate are you measuring that alternates? Q9? If so, that's not a relaible indicator of what's going on with the other gates.
Looks to me like the gates of Q11, Q10, and Q8 just go high impedance when you stop driving the gate of Q9 and it opens. That leaves the gate capacitors on the other three MOSFETs isolated retaining their charge which leaves them on. It appears to me that once you turn Q9 it will cause Q10 on, Q11 off, and Q12 off. And then it will stay that way even after you shut off Q9.
MOSFETs don't just turn off when you disconnect their gate. You actually have to discharge the gate capacitor. You can actually test MOSFETs out of circuit this way by using the multi-meter measurement currents to charge up the gate-source cap and then moving the probes to other pins to test if the source-drain is conducting or not.
Is that what you're seeing? I'm behind on this thread and only skimmed it.
I decided the check the 555 output. On the scope you can see some strange oscillations every low to high transition, it gets worse at lower frequencies. Is this normal behavior? I thought a 555 would give clean square wave output?
I decided the check the 555 output. On the scope you can see some strange oscillations every low to high transition, it gets worse at lower frequencies. Is this normal behavior? I thought a 555 would give clean square wave output?
I assume this is a separate question from the transistor never turning off...
Is it actually worse? Or are you just reading on a different time scale in each graph? Is the frequency of the ringing about the same between both except for the lower frequency it lasts a lot longer?
Because that doesn't look like ringing to me. It looks more like your 555 can't decide between thresholds or something like that.
Is it actually worse? Or are you just reading on a different time scale in each graph? Is the frequency of the ringing about the same between both except for the lower frequency it lasts a lot longer?
Because that doesn't look like ringing to me. It looks more like your 555 can't decide between thresholds or something like that.
I just noticed that your 555 timer is not decoupled. Add a decoupling capacitor across the power pins. You might also want to do the same for the H-bridge itself.
If those don't work, then add a low value resistor (100 ohms or less, maybe even 10) in series with the gate of Q9. I feel like they should not be required though and your problem is something else.