Introduction: Introduction to the 555 Timer

Picture of Introduction to the 555 Timer

This instructable is the first step in my learning to use the 555 timer chip. It alternately blinks two LEDs, and you can change the frequency by changing either the resistance or the capacitance. The 555 is not programmable like an Arduino or an ATtiny. You have to change the values of the capacitors and/or resistors to find the desired frequency. This is also a handy tool you can use to quickly find the right values to set the frequency for another 555 project. If you just want to just blink one LED that will work too. Just leave off either LED and it's 330 Ohm resistor. But two is twice the fun.

You will need:

.

* This capacitor kit will give you enough capacitors to get started. Or use what you have. I just grabbed a handful of different capacitors from my parts bin.

** This resistor kit has all the resistors you will need for this project, and a lot more.

Step 1: Assembling the Circuit

Picture of Assembling the Circuit

Assemble the circuit as shown in the diagram.

The green wire should be long enough to reach the last resistor.

The little dot on the 555 marks pin one. It should be in the upper right corner.

Step 2: Directions for Use.

Picture of Directions for Use.

Move the green wire to the resistance you want to use, the more resistance the slower it will blink.

You can try different capacitors, just put them in the same columns as indicated in the diagram. If you are using an electrolytic the minus side (short lead) goes to the black wire.

You can plug more than one capacitor in. If you do the capacitance adds when capacitors are connected in parallel.

The more capacitance the slower it will blink.

A 10 uF electrolytic capacitor is a good place to start. The blink rate was about 1/2 second with the lowest resistance setting and about 5 seconds at the highest.

With a 220 nF capacitor and the lowest resistance setting the lights were blinking so fast they appeared to be on all the time.

With a 200 uF capacitor and the lowest resistance setting the blink rate was about 12 seconds. When I set it on the highest resistance it was very slow. I can't tell you how long it was, I got bored watching it.

It is okay to change either the resistance or the capacitance while the circuit is running. This seems to be a tough little chip.

Comments

alicialboll (author)2016-11-07

Thanks for the clear overview. I have a tangential question:

Does anyone here know how timers on LED flickering candles work? I'm talking about the timer function with 6 hours on/18 hours off. (EG: https://www.amazon.com/eLander-Lights-Flameless-Candle-1-6-Inch/dp/B00MX1FW1Q) Essentially, the candle lights up around the same time each day--until the battery runs out. I'm trying to create a wreath that runs on the same component, but I don't know what that component is called or how I can go about purchasing/hacking one into my project.

JRV31 (author)alicialboll2016-11-08

I have done similar things in three different Instructables using and Arduino or Attiny85 microcontroller. Maybe the code in these will help you.

https://www.instructables.com/id/MoonLight/

https://www.instructables.com/id/Timer-for-motorcyc...

https://www.instructables.com/id/Timer-for-Automotive-Battery-Charger/

alicialboll (author)JRV312016-11-08

It looks like I'd need to use an Arduino as a power supply in addition to programming the Attiny85, correct? I'm not keen on attaching an Arudino to a project I'm trying to keep this as small as possible, hence my fixation on how those LED candles work. Thanks for pointing out your tutorials--they may come in handy for other projects!

JRV31 (author)alicialboll2016-11-09

the power supply in this instructable will work, just two capacitors and a voltage regulator.

https://www.instructables.com/id/Timer-for-motorcyc...

This programmer

https://www.sparkfun.com/products/11801

is less expensive and much easier to use than an Arduino.

JeanCL (author)2015-10-23

I'm just an old man who took up electronic as a hobby just a few months ago. I've read books "Getting Started With..." etc. I'm doing OK and understanding more and more.Just want to say that Your instructables have been a big help. Thanks and keep them coming.

the_punnisher (author)2015-10-11

We were using the 555 and 556 for adding " chirp identifiers " to our CB radios when that was all the rage during our " Smokey and the Bandit " teenage phase. A small sound was added when we keyed our microphones. Several other people added an echo effect ( using a looped 556 delay pair ). These circuits were designed to fit inside the microphone and the radio rewired to provide the voltage needed to power the circuit. Illegal but fun. If someone asked if anyone was out there, just key the mike. Or if someone keyed their mic, we would just key ours. No more of that " CQ,CQ Is anybody out there? " c--p. People like myselfsqueezed everything into a Pacific Plantronics headset adapter electronics box. We RULED the SFBA in those days...

Your "chirp identifiers" are called "roger beeps" which sound each time that you unkey your mike, and their purpose is to let the other guy know that it's his turn to transmit, obviating anyone having to say "Over" at the end of their transmission!. Blowing a raucous 'raspberry' into your mike immediately before speaking gave a very good effect too...especially if you were running a hefty line stretcher...P.P.P.P.P.P.P.P.P.P..."Roger D!

Nope, our identifiers chirped WHEN WE KEYED THE MIKE. Not after we communicated. This allowed us to ID without being tracked. It's kinda hard to lock on to a signal if it is not there.
I dealt with a lot of " unauthorized " modifications to CB radios. I still have my SBE Sidebander II. I added the now legal 40 channels to my 23 channel SSB transceiver. I also run Double Sideband suppressed carrier and added a " slider " that allowed me and our group to communicate between channels. DSSC was better for the " footwarmers " that were being used. It's too bad some of the BASE OPERATORS ran the footwarmers, as they were easily caught by the FCC. Some of my best work was confiscated by the FCC and I was given a one word bit of advice: " don't "... I'll post pix of the Sidebander II if you wish.

Your "chirp identifiers" are called "roger beeps" which sound each time that you unkey your mike, and their purpose is to let the other guy know that it's his turn to transmit, obviating anyone having to say "Over" at the end of their transmission!. Blowing a raucous 'raspberry' into your mike immediately before speaking gave a very good effect too...especially if you were running a hefty line stretcher...P.P.P.P.P.P.P.P.P.P..."Roger D!

MrMxylptlyk made it! (author)2015-10-12

good one mate. you should post an equation for the period output of the chip! thanks.

dmwatkins (author)2015-10-10

Ok, I looked at your other posts... I see you are already a pro... I didn't mean to insult your intelligence.

JRV31 (author)dmwatkins2015-10-10

I wasn't insulted, and thanks for telling me about www.dipmicro.com. They have very good prices.

dmwatkins (author)JRV312015-10-10

Welcome. I've been buying from them for about 7 years, never got a bad part.

JRV31 (author)dmwatkins2015-10-10

I paid $.95 for that 555.

Dipmicro has 5 for $.93.

dmwatkins (author)JRV312015-10-10

Yeah, I hate to admit it, but I once purchased a single blue LED from Radio Shack for $4.99.... When I found dipmicro, I got 100 of them for $5.25, and they were 3 times brighter... 8000mcd compared to 2600.

JRV31 (author)dmwatkins2015-10-12

I live close to a Radio Shack and I have gone there a few times when I didn't want to wait for shipping, but they are god awful expensive.

dmwatkins (author)dmwatkins2015-10-10

I just checked the price on the LEDs again... much cheaper than when I bought them... now its $4.71 for 200! So you can pay less at dipmicro for 200 than for 1 at Radio Shack... unreal. Oh and make sure you set the currency to your country.

Mike63 (author)2015-10-10

For those that may not know:

capacitor from Pin 2 to ground is C1

put a resistor between pin 6 and pin 7 (which your not using) is R2

put a resistor between pin 7 and voltage is R1

do not connect pin three to the resistors, you can use the following formula to get fairly close to the desired freq.

F = 1 / (0.693 X C1 X (R1 + 2 X R2))

for the output low time you can use this formula, Low Time = 0.693 X C1 X R2

JRV31 (author)Mike632015-10-10

Thanks, I'll try that.

DIY Hacks and How Tos (author)2015-10-10

I love the 555 timer IC. It is so versatile!

dmwatkins (author)2015-10-10

Also, if you are in the US or Canada, I highly recommend www.dipmicro.com for buying electronics parts. Cheap parts and cheap shipping!

dmwatkins (author)2015-10-10

Thanks for sharing! The 555 is such a fun device to play with! Glad you are playing with it! Here's a few ideas for you:

Use a 6 or 8 position rotary switch to connect different values of resistors or capacitors. Great for making a square wave generator.

From old radios, you can scavenge variable resistors (volume knob) and the more rare variable capacitor (radio station tuning).

Hackaday.com ran a 555 contest a few years ago, and it's still in their archive. The winner had an interesting creation he called LeDomino. Look it up!

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Bio: Most of my instructables will be tutorials for Atmel microcontrollers, Arduino, or Raspberrypi. I try to show concepts that you can use in your own ... More »
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