Short beep (from a hi latch)

[eTech]

I made the change you mentioned and added a VR to the circuit.
VR1 250k
R3 100k
C4 2.2uf
View attachment 135732

Did you test on the BB first?


BTW - PCB looks pretty good.

 

[ThomsCircuit]

Did you test on the BB first?

Um. No. I broke that down and put all the components away. I'm pretty certain this is correct. I used a previous schematic as a guide.

BTW - PCB looks pretty good

thank you E. I got this 3mm solder and a flux stick. That and holding my breath made all the difference.

 

[ThomsCircuit]

1.1 * (100k+250k)*2.2uf = 1 second.
Yes i used a calculator

 

[eTech]

1.1 * (100k+250k)*2.2uf = 1 second.
Yes i used a calculator

hmmm...

Remember, the pot value is 250k, that is its value when it is rotated fully for maximum resistance.
Your calculation should consider the pot value at mid position so you can adjust the timing.

To determine the timing range:

100k+1ohm (1 ohm=pot at minimum value) will set the minimum time =
1.1*(100k*1ohm)*2.2uF=0.242 sec.

100k+250k will set the maximum time =
1.1*(100k*250k)*2.2uF= 0.847 sec

100k+125k (125k=pot at mid position) will set the nominal time =
1.1*(100k*125k)*2.2uF= 0.545 sec

 

[ThomsCircuit]

Your calculation should consider the pot value at mid position so you can adjust the timing.

Good advice. I had after I posted did the calculation with a 500k and saw the difference was just about a 1/2 second longer so I did increase the pot to 500k.
Thank you.

 

[ThomsCircuit]

100k+1ohm (1 ohm=pot at minimum value) will set the minimum time =
1.1*(100k*1ohm)*2.2uF=0.242 sec.

100k+250k will set the maximum time =
1.1*(100k*250k)*2.2uF= 0.847 sec

100k+125k (125k=pot at mid position) will set the nominal time =
1.1*(100k*125k)*2.2uF= 0.545 sec

thank you for clarifying this.

They are voltage sensitive devices however, so its important that the input voltage transitions past 70% of the supply voltage for it to be recognized as a high state and 30% to be recognized as a low state.

I read this too. Its true for many ICs. It doesnt need to go to 100% or 0% to activate an IC's input or trigger.