Hello all,
I'm very new to electronics, but right now I need to make a countdown timer for a game (based off "Celebrities" in the show "Sportsnight"), involving various components. Most of what I need to do I already know or can figure out on my own, however my question relates to the actual counting / display ICs.
The timer has to count down from 120 seconds, to 0, and when it hits zero, it should beep / buzz / whatever. Since I don't have a microcontroller programmer, and know very little about them, I figured for now I'd do it the good-ole-fashioned way, rigging up a bunch of IC's together.
What I've come up with is to use three cmos 4510's (up/down decade (0-9) counter with preset) in series (one for the hundredth's place, one for the ten's place, and one for the one's place), then feeding the outputs of each of those "decimal places" into their respective 4511's (BCD to 7-segment display driver), and then into the 7-seg displays.
Am I correct to assume this is how these counters work? The one's digit will count down from 9, to 0, triggering the ten's digit to count down one, which when *it* reaches 0, will trigger the hundred's digit to count down one? My only question would be - how to set the timer to initialize at 120 seconds? (resetting each IC puts it's outputs at 0).
A couple other ideas I had:
I'm very new to electronics, but right now I need to make a countdown timer for a game (based off "Celebrities" in the show "Sportsnight"), involving various components. Most of what I need to do I already know or can figure out on my own, however my question relates to the actual counting / display ICs.
The timer has to count down from 120 seconds, to 0, and when it hits zero, it should beep / buzz / whatever. Since I don't have a microcontroller programmer, and know very little about them, I figured for now I'd do it the good-ole-fashioned way, rigging up a bunch of IC's together.
What I've come up with is to use three cmos 4510's (up/down decade (0-9) counter with preset) in series (one for the hundredth's place, one for the ten's place, and one for the one's place), then feeding the outputs of each of those "decimal places" into their respective 4511's (BCD to 7-segment display driver), and then into the 7-seg displays.
Am I correct to assume this is how these counters work? The one's digit will count down from 9, to 0, triggering the ten's digit to count down one, which when *it* reaches 0, will trigger the hundred's digit to count down one? My only question would be - how to set the timer to initialize at 120 seconds? (resetting each IC puts it's outputs at 0).
A couple other ideas I had:
- Use a standard up counter, but then using a full adder, subtract the "up" count from 120, then displaying that. So, when the up counter is at 0, the output is 120, when it's at 30, the output is 90, etc. Only problem with this is it's somewhat hokey, and I can't figure out how I'd then convert the 8-bit BCD required for that into the 3 7-seg displays.
- Use a microcontroller & multiplex the output to the 3 7-seg displays. The internet has a lot to say about this, so I'm sure I could do it, but I don't have a programmer, and no working knowledge about microcontrollers, and a somewhat limited budget at the moment.