Hi John,
Just seen how things are progressing, you'll have an engineering degree by year end at this rate
. It's exciting, isn't it, once things start working and falling into place? Glad for you, electronics is wonderful fun and great to learn how things work and can be used.
Glad it's working. You need to breadboard the whole design, otherwise it's taking an unnecessarily "unscientific" (and sloppy) risk and therefore, beware unwelcome surprises later.
Is there a power and a ground connection on the breadboard? I just ask as I couldn't really see it, the brown cable is power and yellow is ground, I think.
1a) Follow the schematic provided.
1b) The diodes are all necessary.
2) Lord knows what that capacitor is but it shouldn't be there and is not at all needed to make that circuit work; I've made plenty of timer triggered by longer than acceptable pulse
using a 100pF capacitor in series to know you're doing something weird, no grounded and no floating capacitor should be anywhere on that board... And I'd hazard a guess that if it works like that you may be doing something else weird elsewhere on the breadboard, maybe.
3) Not sure, use a debounce circuit anyway, always good practice.
4a) Honestly, I recommend taking the circuit apart, starting from scratch and putting the two timers on one breadboard, following the actual schematic, not inventing things that aren't on the schematic to make it "work", and especially using red for power, black for ground, whatever colour for inputs, whatever color for outputs - whatever is anything but red or black. Short flat, neat cables help see what one is doing, as are trimmed resistors that lie flush with the board - where possible.
4b) Vast experience of bungle-learning my way through electronics by mostly breadboarding and studying, I would say that at first the breadboard is a rather confusing place, all new things I didn't read more than the pinout about and components I didn't care to understand much and loads of wires and re-checking datasheets for pin numbers when things weren't working and and even then still getting some of them wrong sometimes and connecting things backwards and wires not being in the right holes but seeming so the first time I looked and forgetting to put either a power or a ground cable somewhere and not seeing until an hour later of botching invented solutions that don't work on a correct circuit tells me that once lost in there, any wrong way out looks like the exit and a relief but may not be the right approach. And I thought I knew what I was doing. ...And I still make a lot of mistakes so I'm not being preachy.
4c) I'd really start that again and put a power cable and a ground cable in the breadboard power strip, for starters, but that's just me being finickety.
4d) Follow the schematic provided calmly and meticulously and re-check progress in small stages.
If you really have it working as needed on the final board that'll be made, great, one less thing to do and good for you!
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...Nice video... Not familiar with that song (joke). Good stuff!