Been working on this for a while. Circuits are not my strong point.
Power Source =5.5v dc
The first image is a 4093 NAND that another used helped me with. It changes a dual led from one color to the other and sounds the buzzer for 750ms each time the 5v touch pad is pressed.
The second image is the 5v relay and an NE555. This circuit will engage the coils relay and hold it until C1 discharges. What am I saying. You guys know this stuff. Let me get to the problem I'm having. Well it's more of a concern.
I've connected pin2 from the output of the touch pad and pin4 from the output of the gate (where it connects to the buzzer) when the touch pads trigger goes high it causes pin4 to go high. At the same time the output of the gate goes low sounding the buzzer and pin2 also goes low which triggers and starts the 555. In theory it works but my concern is that the two pins may trigger at the same time causing unpredictable results. My question is can pin4 be delayed? Perhaps with a simple resistor? I've tried to figure this out but not having any luck. I do thank you in advance for your help
Electronic – Trigger & Reset 555 same button
buttonne555
Related Solutions
I believe it is worth trying to connect directly to the spring: you may get more consistent triggering (I would expect it, but no guarantee).
I'd use a small ceramic capacitor instead of a direct connection though, to protect the capacitive sensor from DC and 50 Hz AC currents which may appear in your circuit. It should be anywhere in 1-100 nF range, one terminal connected to the spring, the other one to your relay. I actually expect such capacitor to be present on the PCB in series with the spring, but extra protection can't hurt.
No, it is not correct.
The reset pin is an active-low additional reset line of the flip flop, as shown before (and on the functional description on the 555 datasheet).
Your schematics must be modified. Here's my suggestions (in red).
Basically, the inverter creates an active high-reset. The OR gate allows to reset the flip flop either due to "threshold" voltage exceeded (CMP2 output high) or due to external reset (low) on pin 4. Basically it creates an additional reset input.
Best Answer
Well technically you can use an RC circuit to create a delay to when pin 2 is triggered but a better answer (I believe) is this after a little information: For the 555 timer to work properly, in either astable or monostable mode, pin 4 must be connected to positive voltage (at least 0.7 V according to Datasheet) prior to any input trigger voltage. This is because this reset pin works to disable the 555 timer when it’s held low. So a problem could arise if pin 4 (reset) is made high and pin 2 is made low at same time. To solve this problem, you’ll want to attached pin 4 to positive supply, and just use the pin 2 trigger as you were. When the pin 2 is high, your relay will be off, and only when pin 2 is triggered low, will the relay be on for the brief period determined by RC circuit attached to 555 timer.
Also if you want to really want to give your piezo buzzer a 750ms on time, then you should consider removing the R1 and C1 connected to the nand gate. Instead connect the output of touch sensor to nand gate (connected as NOT gate like you have) then connect the output of that nand gate to pin 2 of a second 555 timer which is configured in monostable mode with RC network to give a 750ms period. Hope this helps.