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this is an instructable how to make a timer circuit.
what you need:
resistors
500k(variable)
10k
10k
100k
other
bc547b
bc547b
220 uf cap
led
switch

Step 1:

once you have all the parts you can solder everything together and make the circuit.
it's verry handi to have a soldering iron with the proper equipment :p
BE CAREFUL WITH THE TRANSISTORS THEY CAN GET DAMAGED BY THE HEAT OF YOUR SOLDEREING IRON!!

Step 2:

once everithing is soldered together you can test the circuit bij puching the switch and watch what happends. you can change the time with the potentiometer(variable resistor). have fun and be safe.
<p>So... doing a very quick analysis in my head... You push the push button, C1 discharges, you release the push button, C1 starts charging controlled by R1 and P1, driving the Darlington pair which eventually should light up the LED?</p>
Given your components, what range of &quot;time&quot; can you expect on this circuit?
can you make this timer act like a electric swich. i mean it lets the eclectric pass after the time hit 0:00 <br>if its possible email me the plans pleas, thanks :))) <br>arsalanmzz@gmail.com
Nice, but if you want to teach, you need to explain how and WHY the circuit works. Identifying the value of R3 as 100k intsead of 100R would be helpful also. <br>Explaining the cascaded transistors as a Darlington Pair and the benefits would be a plus as well. This circuit is very useful for explaining how transistors work, how to bias them and why, as well as how R-C circuits generate a timing function. Anyone can sockpuppet a circuit, but unless the &quot;student&quot; understands it's operation, true learning has not occured and troubleshooting (the ultimate test of knowledge) will be difficult if not impossible. Don't mean to be critical, but I had an electronics &quot;teacher&quot; in jr. high that couldn't answer any of my questions. While he could make a circuit work, he left me with confusion which delayed my electronics career for 5 years. Things are a lot more fun when your understanding progresses beyond the &quot;black box&quot; stage.

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