LED Chaser Circuit Without IC

Intro: 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).

Video tutorial

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.

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?

Video tutorial

Comments

[MarkRRichards]

This was a fun project to get some soldering experience. I used 2n2222 transistors and 5K resistors. Maybe that's way it didn't start rolling until I shorted a base to an emitter. What changes would I need to do to make this work on 3.2V? Thanks

[Yuhoo1]

In my opinion, the LEDs would light up when the transistor is OFF and not when the transistor ON. Correct me if I am wrong,

[charlessenf-gm]

Brilliant construction - artistic! Saved the schematics and added this to a ToDo List sure to extend beyond the few years left me! Thanks, enjoyed reading your Instructable

[bf1104]

Hi... As everyone else has said, it's a great looking project. I have a quick question if you don't mind? How would I go about slowing down the switching from one set of leds to another?
Thanks in advance

[tim.g1zlh]

Change the 100uF caps - smaller values will make it go faster, larger values slower.

[charlessenf-gm]

Could you use different values for each color led?
And expect . . . what then?

[bf1104]

Thanks 👍👍🙏

[Euticus]

So, essentially, you built the discrete equivalent of an IC.

[imperf3kt]

I would say no, they've built a circuit out of discreet parts, but an integrated circuit that dies not make.
The "Integrated Circuit" wasn't invented until 1961, but circuits were built before that using discreet parts, why are they not considered retroactively named ICs?

[charlessenf-gm]

I recall thin, rectilinear circuits encased in mustard yellow (ceramic?) material with a number of leads emanating from one edge and assumed they contained tiny discreet parts I could only imagine.

Isn't an IC a device that contains the materials of 'discreet parts' and of conductive 'traces' that are simply microscopic in dimension?

[YLBright]

I would say, yes. It is not an IC, but it IS an equivalent. Congrats. Nicely done. I like it.

[RANDOM KNOWLEDGE]

YUP LOOOOL

[newusername1]

Does the forward voltage of the different colored leds have to be similar?

[bruceyheli]

How many LED’s per row can be added?

[johngovardhana]

Very good performance, very nice project,go ahead.

[john.ostermann]

Can anyone answer this: if you chose to run it off of a 12V system, as in a car, would any component/s need to be changed bc of increased voltage (12V vs 9V)?

[tim.g1zlh]

The current limit resistors (330R) will need to be a teensy bit bigger to keep the current under control. Top of my head, 470R should be fine. The rest of it, well, nothing there to get fussed about. Play - it's a very simple circuit.

[Mad4400]

You might raise the value of the 3 x 330 Ohms resistors to 470~510 Ohms to protect the LEDS from over current..

[Mad4400]

Thanks for providing a schematic with your project this time. Typically the convention is V+ at the top and ground at the bottom. Following this rule, I have redrawn it for you.
https://i.imgur.com/iNf18ds.png

Ignore the comments from the "clever" people, if they were truly intelligent they would have offered some helpful input.

A discrete device (or discrete component) is an electronic component with just one circuit element, either passive (resistor, capacitor, inductor, diode) or active (transistor or vacuum tube), other than an integrated circuit.

[Rukbat]

Thanks for the schematic, Mad - saved me the trouble. The original was definitely a schematic, but your redo made it clear at a glance that this is a ring oscillator. (And ... an integrated circuit is 2 or more things integrated [usually] on the same silicon die, which is why a transistor doesn't qualify.)