0–9 counter on a 7-segment display: 555 → 74HCT393 → 4511
Open in the lab ▸Make my own copy
A complete little digital system. A 555 gives a 2 Hz clock; a 74HCT393 binary counter counts it; a 74HC08 AND gate spots the count of ten (binary 1010) and resets the counter to 0; a 4511 decodes the four bits into the seven segments of a common-cathode display. A 7805 makes the 5 V the logic needs from a 9 V battery. Why HCT and not HC: a bipolar NE555 on 5 V only gets its output up to about 3.3–3.6 V, and a 74HC input needs 3.5 V to be sure it sees a 1. Fed from the 555, an HC393 sometimes counts twice. The HCT version has TTL-level inputs (anything over 2.0 V is a 1), so it counts every tick once. (A CMOS 555, the TLC555 or 7555, would also fix it.) The 4511 shows 6 and 9 without their tails, as the real chip does. Try it: wire the AND gate to Q0 and Q2 instead (binary 0101) and it counts 0–4. Or take out the reset wire and watch the 4511 blank the display for 10–15.
What is on the bench
30 parts, 62 wires.
| Electrolytic capacitor | 3 |
|---|---|
| Resistor | 2 |
| 9 V battery | 1 |
| 7805 regulator | 1 |
| 555 timer | 1 |
| Ceramic capacitor | 1 |
| 74xx393 | 1 |
| 74xx08 | 1 |
| 74xx4511 | 1 |
| 7-segment display | 1 |
Put it on your page
The project runs live inside the frame: readers can press buttons, turn knobs and read the meters.
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Link
https://zencircuitlab.com/p/zclcount09
Published by its author under the lab's community terms: it may be opened, copied and changed by anyone. Simulation results are for learning; check a real build against the parts' datasheets.