Introduction: LED Chaser Circuit Without IC
In this Instructable I show you how to make a simple LED chaser circuit. The special thing about this circuit is that it does not use an IC (Integrated Circuit).
By using different resistors, capacitors and transistors, I succeeded in this project to make a circuit that lights the LED lights one by one. The base of both the transistors are connected to + connection through resistor. Any one transistor will get activated first. (this is because no transistor is exactly similar to other one). Lets assume transistor 1 turns on first. When the transistor turns on the collector pin gets grounded and led at its collector lights up. Also the capacitor starts to charge through ground provided by 1st transistor and the 4.7 K resistor at the base of 2nd transistor. Since the 1st capacitor is charging it is taking current from the 4.7 K resistor which is at the base of 2nd transistor. The base of 2nd transistor has no current to activate its led. At some point 1st capacitor will charge up. And when it does so, there is no more current flowing through it. Now there is enough current that can flow through base of 2nd transistor. The 2nd transistor gets activated. (Including the led connected to its collector). The process repeats and when the 2nd capacitor is charged the third transistor is activated. Then the first, second and so on.
- 3 x 3 LED lights (any color you want)
- 3 BC547 transistors
- 3 330 Ohm resistors
- 3 4.7 K resistors
- 3 100 uF capacitors
- Electrical wire (small pieces)
Step 1: Connecting the Transistors
For this project I used BC547 NPN transistors. In the attachments is an image with the pin assignment to keep it clear. Bend the collector and base connections of all 3 transistors to the left. Bend the emitter pins to the right and solder them together.
Step 2: Mount the Capacitors
As described in the introduction, capacitors are placed between the transistors to "control" the circuit.
- Solder capacitor 1 + to the collector of transistor 2
- Solder capacitor 1 - to the base of transistor 1
- Solder capacitor 2 + to the collector of transistor 3
- Solder capacitor 2 - to the base of transistor 2
- Solder capacitor 3 + to the collector of transistor 1
- Solder capacitor 3 - to the base of transistor 3
Step 3: 4.7K Resistors
Solder a 4.7K resistor to all 3 base connections of the transistors. Connect the other ends of the resistors together.
Step 4: 330 Ohm Resistors
Solder a 330 Ohm resistor to all 3 collector connections of the transistors. Connect the other ends of the resistors together with the ends of the resistors from step 3.
Step 5: Prepare the LEDs
Because I like it looking I chose to mount the LEDs in a kind of star shape. Of course this can also be done in a straight line or another shape.
Solder the LEDs together per group of 3. Note that the anodes and cathodes are in the same direction.
Then solder the cathodes (-) of the three groups together.
Step 6: Connect the LEDs to the Circuit
Solder a red wire to the 3 plus connections of the LEDs. Solder a black wire to the joint minus connection of the LEDs.
Solder the other ends of the red wires to the collectors of the transistors. Sequence determines whether the sequence of the LEDs is left or right (reminds me or switching phases XD)
Solder the other end of the black wire to the connected emitter terminals.
Step 7: Connecting the Battery
Solder the red wire from the battery connector to the connected ends of the resistors. Solder the black cable from the battery connector to the connected emitter terminals of the transistors.
Step 8: Ready
Ready! Just click on the battery and the LED chaser will work!
The electrical diagram is in the appendix.
With the last few Instructables came the question for an electrical schematic of the circuit. Since I have no experience with drawing diagrams, I am very curious about what you think of this! Is this scheme well drawn and is it useful to you?
This is an entry in the
Make it Glow Contest