How to delay a LED?? (On/Off)

I need to at least delay my LED.

I'm ONLY allowed to use BJT and resistors. ( No Diode, Relay, Capacitors and IC's etc.)

Details: there are 7 LEDS in total.

There are 7 levels in the container which the led's indicate.

If the container is "empty" the 1st led is "on".

If the water reaches to the 2nd led/level, "on" and the 1st led will turn off.

3rd led/level = On ; 2nd and 1st = Off

4th led/level = On ; 3rd, 2nd, 1st = Off

5th led/level = On ; 4,3,2,1 = Off

6th led/level = On ; 5,4,3,2,1 = Off

If the water reaches to 7th led/level all led's is "Off" but after a delay in (secs, milliseconds) all the leds will turned "On"

I need any kind of help or advice to do this project. thankyouu!

by amsnklmf
March 13, 2019

resistor and transistor don't have delay function.

by wangwg88
March 13, 2019

3 Answers

Answer by amsnklmf

Please help

+1 vote
by amsnklmf
March 13, 2019

I couldn't attach picture of circuit. you can tell me your email.

by wangwg88
March 19, 2019

Answer by wangwg88

you may use millions pieces of BJTs and resistors to make the delay circuit, but it never happens in actual circuit.

+1 vote
by wangwg88
March 17, 2019

Answer by Negativ3

Needs a timer circuit on the output to LED 6 so when it goes off (LOW), the timer is initiated, then "enables" all LEDs after a pause. Difficult to be more exact without seeing a circuit diagram Have a look at 555 timers.

+1 vote
by Negativ3
March 23, 2019

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