But Sensor two acts a "proximity dimmer" which is cool, but still not quite right.

What does that mean?

 

Can you explain what it is doing?

 

This site supports videos uploaded to YouTube

 

I'll pick this back up tomorrow - super late here now. Thanks to everyone for the help so far.
As it happens I started a YT channel a week ago or so. I will upload to there and link the page to here.
I'm sure I have something miswired still.. Ordering some breadboard for future projects.. doing it like this is a nightmare

 

One last though. This is how it should be wired:

 

You will need a reverse-biased diode (cathode to Vcc, anode to Q3 drain) connected across the solenoid to protect Q3 from the back-emf spike when Q3 switches off.

 

You will need a reverse-biased diode (cathode to Vcc, anode to Q3 drain) connected across the solenoid to protect Q3 from the back-emf spike when Q3 switches off.

Yes, will do. Due to the rapid cutoff, and high voltage transient generated by the bEMF, I will use a bridge of 1n5408's to capture the wasted energy and store it in a capacitor.

Hence why I want to drive the solenoid via this particular MOSFET in a Darlington / Sziklai arrangement (It's the latter I believe?) which has an appropriate clamping action and given the BJT will cut off faster than it would otherwise, due to the increased gain, giving me that potential to charge the cap. Still learning lots but that's the idea. Increase the efficiency of the oscillations any way possible.

 

One last though. This is how it should be wired:
View attachment 287933

That's awesome, thanks! I'll update the circuit and let you know how it goes.

 

Slight modification. Added C1 to prevent circuit latching ON when power is first applied.

 

Slight modification. Added C1 to prevent circuit latching ON when power is first applied.
View attachment 287977

Is that a ceramic/tanatalum/Electrolytic?

I presume ceramic if it's in series like that?

Thanks again for the extended help

It really helps me understand what each component is doing, and how.

 

Is that a ceramic/tanatalum/Electrolytic?

All three choices are fine. It's not in series but in parallel with the base-emitter of Q2

 

All three choices are fine. It's not in series but in parallel with the base-emitter of Q2

Interestingly, the latch DOES work without the capacitor. Adding it now because I have to FULLY magnetize the second sensor (ie. make the LED turn fully off, then it stays off) Both the same thing, 44E-402.

 

Interestingly, the latch DOES work without the capacitor.

Correct but sometimes with my circuit on the breadboard it latch ON when first powered up. I verified your issue and since have moved the cap to the base of Q1 and ground. You can leave the cap out if not experiencing the problem I had but be aware if it does.

 

 

Having now built the circuit in the video and studied it a bit I understand what's happening a lot better.
I need to use 3 sensors instead of 2.

I want H2 to switch solenoid supply off (as it already does)
-But simultaneously cut off supply to an "H3", and then H1 should switch H3 back on.

H1- Switch on supply to H3
H3- Switch on supply to Solenoid
H2- Switch off supply to solenoid AND H3


Can I switch both Solenoid and H3 low side off a shared "Sziklai arrangement" (?) (Both Negatives into same transistor)
Or do they need separate arrangements?

 

You will need two identical latch circuits composed of Q1,Q2 and Q3,Q4.

 

You will need two identical latch circuits composed of Q1,Q2 and Q3,Q4.

Thankyou for your time and effort, it means a lot. This will allow the whole thing to work.
I'll share a the YT video video link to this thread when it's done.

Hopefully all this info will be of use to future visitors, too

 

..What are the resistor values in the most recent schematic? All 10k? (last-last question-lol)

 

10k OK

 

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