555 chip help - Page 1
Forum section: electronics / beginners

author: shane_95
author_rank: Regular Contributor
timestamp: July 06, 2012, 02:26:14 pm
content: Im thinking about making this CONTINUITY TESTER, but im a bit confused as to where pin 7 of the 555 goes off to?Also with the capacitors, what is 10n? is that 10 uF

author: G7PSK
author_rank: Super Contributor
timestamp: July 06, 2012, 02:36:02 pm
content: Pin 7 is not used and 10n is ten nano farad or 0.001 micro farad, this is a link to a conversion chart, print it out to help you memorize it.http://www.electronic-supply.com/capconversion1.htm

author: olsenn
author_rank: Frequent Contributor
timestamp: July 06, 2012, 02:36:33 pm
content: According to this schematic, pin 7 is floating, so don't connect it to anything.

author: w2aew
author_rank: Super Contributor
timestamp: July 06, 2012, 03:43:59 pm
content: Quote from: G7PSK on July 06, 2012, 02:36:02 pmG7PSK made a typo... 10nF is 0.01uf

author: IanB
author_rank: Super Contributor
timestamp: July 06, 2012, 04:16:30 pm
content: Background info:http://en.wikipedia.org/wiki/Nano-

author: G7PSK
author_rank: Super Contributor
timestamp: July 06, 2012, 04:25:44 pm
content: Whoops so I did.

author: 6502nop
author_rank: Regular Contributor
timestamp: July 07, 2012, 10:39:05 pm
content: That's way too many parts for something so darn simple.How 'bout three resistors, one transistor, one buzzer (Radio Shack #273-059), and a 9V battery snap? See attached.It'll work down to the minimum voltage of the buzzer + 0.6V (for the buzzer given, that'd be 6.6V-18.6V) at about 15mA when buzzing. So, a 9V battery would last a long time. I built this as a water alarm for a sump system, but it works pretty darn well as a continuity tester. In fact, I put this in a small box and used it when I was fixing Power Wheels ride-ons.nop

author: shane_95
author_rank: Regular Contributor
timestamp: July 08, 2012, 08:04:01 am
content: Quote from: 6502nop on July 07, 2012, 10:39:05 pmThat seam really easy, 1 question, where Domino's connect the ground leads to?

author: LEECH666
author_rank: Frequent Contributor
timestamp: July 08, 2012, 08:55:21 am
content: Who the hell is " Domino's"?I think you're talking about the reference symbols in the shematic.This symbols means that all parts this symbol is connected to get connected together.Hope that helps.Cheers,Florian//EDITAlso note, that you have to use a buzzer here, a speaker wont work for the second circuit. So if you only can find a speaker in your junkbox stick to the NE555 circuit.

author: shane_95
author_rank: Regular Contributor
timestamp: July 08, 2012, 10:55:14 am
content: Quote from: LEECH666 on July 08, 2012, 08:55:21 amwoops, auto correct on my ipad

author: shane_95
author_rank: Regular Contributor
timestamp: July 08, 2012, 11:00:43 am
content: i can get buzzers for about a buck so ill probably use one, if not is this speaker good enough?

author: vk6zgo
author_rank: Super Contributor
timestamp: July 08, 2012, 01:18:34 pm
content: Quote from: shane_95 on July 08, 2012, 11:00:43 amIt will work for your original 555 circuit,but not with6502nop's circuit,where it will only go "click!".A buzzer is different from a speaker,as it generates its own tone on connection of a dc supply.PS:Actually,some buzzers need to be driven with a tone to operate,just like a speaker,but the kind for that circuit has its own internal tone circuit.Also,have a look at Mint's thread "How to chose a buzzer?"

author: shane_95
author_rank: Regular Contributor
timestamp: July 08, 2012, 01:59:38 pm
content: Quote from: vk6zgo on July 08, 2012, 01:18:34 pmi meant if i cant use a buzzer ill use the other circuit

author: 6502nop
author_rank: Regular Contributor
timestamp: July 09, 2012, 12:20:44 am
content: {Sigh}Okay, Shane, let's try a little "Eddy Electron" here. Follow:In order for a speaker or piezo element to make a noise, you first have to move the diaphragm in one direction, then the other (with a piezo, it just springs back on it's own, and speakers will tend to fall back to a "zero" position, but can be pulled back quite a ways). This requires an AC waveform, or for the piezo, a square wave can be used.Since the output of the 555 is on or off, there is no "wave", unless you're switching it very fast. So, if you wire up the 555 in astable mode (always producing a running square wave output), then it is perfectly capable of driving the speaker (through a capacitor to offset the DC) or piezo.Problem is, the 555 only has the one output. So, in the original circuit posted, the 555 isnotthe continuity checker, but the speaker/piezodriver. The two transistors are actually the testing circuits that trigger the 555 on. So, if you have the buzzer/piezo that has abuilt-indriver, you don't need the 555 and extra components, as my posted circuit shows. All you need is to turn on the base of the transistor, and the transistor then turns on the buzzer/piezo. If you decide to use the undriven buzzer/piezo, then you'll need some sort of oscillator, which goes back to your original circuit, as that's what the 555 does.Got all that?Dumb and dumber version: The piezo with built-in driver is like an automatic transmission. The standard piezo is like a manual-shift. My circuit uses an automatic, your circuit has to do the shifting.QuoteA very popular pizza chain here in the you-ess-of-ay. In fact, they got started here in my home state.nop

author: 6502nop
author_rank: Regular Contributor
timestamp: July 10, 2012, 04:41:45 am
content: Update: I just posted some more info on piezos (et. al.) in Mint's "How to choose a buzzer" thread. The diagram also covers speakers and transistors wired to pin3 of a 555.nopI hate re-inventing wheels...