# A 555-Based, Two-Channel Remote Control Circuit

[fahadshihab], a young tinkerer, shared his circuit design for a simple remote control using 555 timers.  Using a 555 calculator, he designed a clock circuit that would run at 11.99 Hz. Two transistors are connected to inputs (presumably button switches). One sends the plain clock signal, and one sends the inverted clock signal. A matching circuit at the other end will separate the channels. All it requires is connecting the two circuits in order to synchronize them. It would be easy enough to interface this with an oscillator, an IR LED, or a laser for long-range control.

The great thing about this circuit is its simplicity. It’s often so easy to throw a microcontroller into the mix, that we forget how effective a setup like this can be. It could also be a great starter circuit for a kid’s workshop, demonstrating basic circuits, timers, and even a NOT gate. Of course, it would be a good refresher for those without a lot of circuit knowledge too. Once you’ve mastered this, perhaps an AM transmitter is next?

1. Harvie.CZ says:

Inverted signal for second channel? What if there’s phase shift between tx an rx oscillators? that would swap channels… Or there is duty cycle different from 50% to tell which signal is inverted and which is just phase shifted by 1/2?

Schematics aren’t much intuitive…

• Richard says:

You’re right.

It describes the standard 555 clock oscillator for the transmitter, and in the last sentence of that section, says, “Also you will need to build one more for the receiver.” So the description clearly implies having two identical free-running 555 timers.

There is no mechanism to keep them in sync, and 555 RC oscillators aren’t very stable or precise, so they will very quickly drift wildly out of sync. Your idea about the duty cycle would only work if the receiver were detecting the duty cycle and adjusting the clock somehow.

I can’t imagine this working well without a mechanism for syncing the clocks.

• Stoneshop says:

Yes. You’d need a PLL to regenerate the clock at the receiver; from there it’s easy enough to detect, say, 30% or 70% duty cycle.

BTW, a 555 oscillator as shown here won’t run at 50% duty cycle, though for practical purposes it’s good enough. Connecting 2 and 6, capacitor from 2+6 to ground, resistor from 2+6 to 3 will give you 50%, save a resistor and simplify the calculation.

• Michael says:

Sounds like an example of building something, powering it on for a minute, and declaring that it works, without additional testing. Since his pictures show everything on one breadboard, I think it’s reasonable to assume that he powers the whole thing (both circuits) at once, so probably the 555s are, more or less, in sync to begin with.

I certainly applaud the effort. Seems like a pretty good start by someone without a ton of experience. Better than the sort of stuff I did early on. I do agree that it’s not really up to the standard of most things we see here.

2. SYNTRONIKS says:

Unsure if this is hackaday quality material.

• Anne Nonymous says:

This is the “test” that hackaday applies for all incoming submissions:

-Does it have a 555 timer? [50 pts]
-Does it use an Arduino [100 pts]
-Does it fill an “invented” need [50 pts]
-Does it blink an LED [25 pts - 50 pts if it's for aesthetics only].
-Does it have a lot of wires [10 pts]
-Does it use a breadboard or protoboard [10 pts]
-Does it use any parts, even tangentially connected to sponsors [100 pts]

Articles need at least 20 points to get posted, so yeah, it meets the HaD test.

• Mike Szczys says:

You really underscored the value for wire-porn and use of breadboard. We also score highly for projects that serve absolutely no purpose.

• vonskippy says:

Ah, that explains the bazillion clock, pov, or pov clock projects.

//just kidding//

• Ralf says:

You forgot: putting “without IC” in the title and then using 2 ICs as the primary components. ;)

• Cheapskate says:

He is only 14 years old though.

• SYNTRONIKS says:

I’ll tell you hwat: That’s significantly better than I was at that age. I was still trying to understand ‘ground’. Good for him!

• potatoman412 says:

Exactly- kudos to him for getting in there and building something. 555s are a wonderful place to start. It’s not like he is out there getting someone pregnant or hitting mailboxes. Hope he continues despite some of the other comments on here. Also, kudos for keeping the Arduino on the shelf for this one :) Keep on tinkering :)
@SYNTRONIKS yep same here. Took me a bit to learn that the color of the wire is not always anything close to an indicator, so the multi comes out to measure twice, attach gator clip once :) Good times…

• Tony says:

555s are superb parts.

I once need a mouse that would click it’s left button automatically (like the old autofire joysticks) so 555 was the go. (Shush old timer, yeah yeah use a RC circuit.)

I wasn’t working, polarity was ok, and it was getting hot. Hmm.

Replacement 555 did the same thing. Hmm x 2.

Yeah, probably should have the polarity on the meter leads first…

Both 555s survived, and are still happily working.

Awesome part!

3. big billy says:

Sure, it isn’t properly engineered but as pointed out, kid is 14 and is putting out better work than other teens glued to their phones. I wouldn’t knock him at all for it. Never make fun of someone for how little they know.

• Nick Johnson says:

I don’t think anyone’s making fun of the author – just critiquing the solution. And that can’t be out-of-bounds based on age, or he’ll never learn anything!

4. Will Morris says:

Well you might want to work out a circuit to switch the 555 between two different frequencies. This is called Frequency Shift Keying. The receiver can separate them with complementary high and low pass filters.

The phase inversion method is fine for a momentary toggle switch but interference or loss of signal will cause spurious toggling.

• arachnidster says:

That’ll communicate one bit fine, but I believe the goal was to communicate two bits.

• Stoneshop says:

FSK will work fine signalling two events. At the receiver you’ll need to differentiate between no events (no signal), event #1 (low frequency signal) and event #2 (high frequency signal). It’s easy enough getting a 555 to generate different frequencies, by switching a second capacitor parallel to the frequency-determining one. The receiver would get a bit more complex; I would use a PLL (say, an NE565) to determine high or low frequency, plus some stuff to detect whether there’s signal at all.

• arachnidster says:

You need to detect both signals at once, too. Thanks for mentioning NE565/LM565, though – looks useful.

• Tony says:

Play with the LM567 – tone decoder- as well.

5. Anne Nonymous says:

I should have posted every experiment I did from my 300:1 electronics kit from RadioShack.