Need help designing a counter circuit. (I don't have a lot of experience designing circuits)

[Spencer01]

I am currently designing a counter circuit, however, i keep running into issues and a point in the right direction would be greatly appreciated.

Components I want to include: - a 7-segment display and 4026 - a PICAXE and/or a 555 IC (the PICAXE would be used to turn the device off without resetting the 7-segment display) - an LED to show that the device is on - three switches: one to reset, one to turn off/on the device and one to add to the count - possibly a piezo buzzer to read the count on the 7-segment display (?)

I have attempted to make this circuit (it is attached) but did not get very far. Again, any advice would help, thanks.

 

[AnalogKid]

First, easy parts.

1. Each segment of a CD4026 goes high when active, but can source only a few MA. Driving the display directly is not recommended if any real brightness is needed. but it will work dimly for verifying that the rest of the circuit works.

2. My guess is that the 555 is in there to debounce the count switch so you get only one count per press - correct? If so, you can use the monostable circuit in the 555 data sheet to fill in the rest of the components.

3. Why is the output of the 555 connected to a switch. If the 555 output is low when the switch is pressed, this will damage the chip.

4. What is the function of the PIC? Please add it to the schematic, even if it is only a block with a couple of signal wires.

ak

 

[The March Muppet]

One point at a time.

would be used to turn the device off without resetting the 7-segment display

If the 4026 loses power, the count is gone - period. You could enable the blanking input to extinguish the 7 segment display though.

three switches: one to reset, one to turn off/on the device and one to add to the count

The reset is straightforward. Bring the reset pin high and the count goes to zero. No need for switch debouncing.

On and off the entire device? As earlier stated, if you wish to store the count, the 4026 will require power.

Adding one to the count will require a debounced switch (just like it sounds - mechanical switch contacts will physically bounce before coming to rest. The counter is fast enough to see this bounce as a series of valid pulses) - look up switch debouncing. If you need to manually insert a count "into" an existing clock line, then you can do so with small signal diodes.

possibly a piezo buzzer to read the count on the 7-segment display (?)

Don't understand. Do you mean a single beep every time the count is incremented, or (say) - at the push of a button have the buzzer beep 7 times if the display is 7?

Assuming the former. although integrated piezo buzzers do exist, the bare disk type will require an oscillator.

To just chirp, a piezo "buzzer" (with integrated oscillator) would require at least a transistor (so as not to load the clock signal) - a sustained beep would require a time delay, like a "one shot".

If you just have a bare disk, a 556 dual timer could do the buffering, one shot, and oscillator duty.

but did not get very far.

How far? Noting that the purpose of and connections to, the 555 on your diagram is all forked up, as well as why are you pulling the output low,

What is it supposed to be doing? If continuously counting, then it has to be wired as an "astable multivibrator". If just debouncing the switch, "non resettable one shot".