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I have 5 LEDs in an array, which I need that when I press the power button, they turn on in sequence: the first one turns on and stays on, then the 2nd led turns on and the 2nd one stays on and so on with the third led until the 5th one. Once the 5th one turns on, they must stay on until I press the off button. The cycle is repeated when the circuit is turned on again.

I have done some research, and they all use 555's to do this, but it restarts the cycle automatically.

I have also thought about doing it with cascaded transistors, so that when I turn on the first one, it lets the power go to the second one. And the time delay I would get with a capacitor. But the problem is that I don't know how to calculate the transistors I need.

Context: 5 IR LEDs of 1.45 V and 50 mA. 1 battery of 1.5 V and 3 A. On/off button.

Example

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  • \$\begingroup\$ Concentrate on asking a specific question please. \$\endgroup\$ Commented Jun 8, 2023 at 8:59
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    \$\begingroup\$ Sounds like a job for a Johnson counter or an MCU. \$\endgroup\$ Commented Jun 8, 2023 at 9:31
  • \$\begingroup\$ Who are "they"? I'd do this with a microcontroller. \$\endgroup\$ Commented Jun 8, 2023 at 13:22
  • \$\begingroup\$ To fabricate the LEDs? I am not sure that's the word you meant to mean there. \$\endgroup\$ Commented Jun 8, 2023 at 13:42
  • \$\begingroup\$ "they" refers to another web tutorials \$\endgroup\$ Commented Jun 8, 2023 at 16:06

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A shift register like 74HC164 filled with "ones" on serial input clocked from 555 will do the job.
After 5 clk stop the clock.
However, for 1.5V battery supply you will need to add a DC/DC converter.

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  • \$\begingroup\$ The complicated part is stopping the clock after five pulses and prefilling the shift register. \$\endgroup\$ Commented Jun 8, 2023 at 10:19
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    \$\begingroup\$ @MarcusMüller When the fifth Led is ON clamp the Clk wire with transistor or disable 555. \$\endgroup\$ Commented Jun 8, 2023 at 10:26
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    \$\begingroup\$ Would be cool if you describe that in your answer, not just the comment here :) also, does the proposed shift register sink or source the current you need (haven't checked myself)? How about solving the initializing problem? \$\endgroup\$ Commented Jun 8, 2023 at 10:28

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