clap circuit  - Page 1
Forum section: electronics / beginners

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 01:05:54 am
content: i need help with this circuit pleasehttp://circuiteasy.com/clap-switch/i got 2n3904 replacement transistor for all the bc transistors they are all npn that i got i made it on a solderless breadboard and the circuit was not workingi need help before saturday i appreciate all the help

author: dr.diesel
author_rank: Super Contributor
timestamp: March 06, 2014, 01:13:47 am
content: Quote from: electronics technician on March 06, 2014, 01:05:54 amWhat happens on Saturday?

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 01:17:21 am
content: i will submit it in class to get graded on it i dont want to fail just because it was not working

author: dr.diesel
author_rank: Super Contributor
timestamp: March 06, 2014, 01:21:11 am
content: What will you learn if I give you the answer?

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 01:23:51 am
content: im frustrated with this circuit i have been on this for almost a month now trying different combinations of pinouts and still no working project

author: minibutmany
author_rank: Regular Contributor
timestamp: March 06, 2014, 01:46:53 am
content: This doesn't really look like the best circuit to be poking around in if you don't have experience with mains.

author: Nerull
author_rank: Frequent Contributor
timestamp: March 06, 2014, 01:54:16 am
content: 120VAC is lethal. It can and will kill you if you aren't careful.

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 01:56:26 am
content: thats not the point i need help with this clap circuit please help btw

author: c4757p
author_rank: Super Contributor
timestamp: March 06, 2014, 02:01:28 am
content: The circuit will work fineoffmains too -pleasemove off the mains to test this further.Take a photo so we can see what's wrong.

author: Nerull
author_rank: Frequent Contributor
timestamp: March 06, 2014, 02:02:47 am
content: It is exactly the point. You are playing with a circuit you don't understand, with dangers you don't understand. That is, to put it mildly, incredibly stupid. Your teacher should fail you for that, to discourage other students from putting themselves in danger.And please, for the love of god, tell me you aren't routing 120VAC through a breadboard.Pick a project less likely to get you killed, your parents and teachers will appreciate it.

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 02:10:06 am
content: you dont understand its my teacher that gave my class this project to do but im having problems with getting it working can you helpi was never going to run 120v ac though a bread board

author: kizzap
author_rank: Unknown
timestamp: March 06, 2014, 02:15:39 am
content: Things: people around here don't like people playing with mains if they don't know what they are doing. 120V mains, while lower then other country's mains voltages, is stilllethal.That said, from the schematic, the mains looks like it could be completely isolated from any breadboards. Please ensure you fuse mains.You also need to tell us what tools you have at your disposal.What I would suggest doing, is to break the circuit down into blocks on your breadboard, (and start off not having it powered from mains) first thing I would get working is the microphone input. If you have a scope, try see if you can trigger off the collector of Q1, to ensure that side of the circuit is working, then add in additional parts to the circuit.

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 02:19:37 am
content: i dont have a scope yet unfortunately but i have a dmm and everything i need to solder it to a perf-board

author: kizzap
author_rank: Unknown
timestamp: March 06, 2014, 02:53:26 am
content: does the meter have a min/max mode?

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 03:03:55 am
content: http://www.transcat.com/catalog/productdetail.aspx?itemnum=DM-210this is the one i have thinking about switching to fluke next time

author: LektroiD
author_rank: Frequent Contributor
timestamp: March 06, 2014, 03:20:25 am
content: Quote from: electronics technician on March 06, 2014, 01:05:54 am2n3904's are different pinout to BC's. Check the datasheets.

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 03:30:29 am
content: the pinout of the 2n3904 is EBC correct me if im wrong

author: LektroiD
author_rank: Frequent Contributor
timestamp: March 06, 2014, 03:36:39 am
content: depends which way you look at it (check the datasheets for both). What's the BC you're substituting?

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 03:52:57 am
content: with the flat side facing you it was EBC but like you said it depends on how you look at iti got this replacement for all the bc548 and bc368so i have 4 2n3904 npn trannies

author: kizzap
author_rank: Unknown
timestamp: March 06, 2014, 04:01:36 am
content: You realise that different transistors have different gains right? so the circuit won't function as intended with the wrong transistors, without recalculating the biasing on each of the transistors.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 06, 2014, 04:03:02 am
content: Quote from: kizzap on March 06, 2014, 02:15:39 amI would second the suggestion----This isn't really a high frequency circuit,so you should be able to check the Bistable & the other stuff with any old DMM.The only place you may have problems is with the mic circuit,because the pulse caused by the "clap" is only of short duration.The circuit operation description on the website is pretty lousy,& I can maybe do better,so here goes!Assume initially,thatQ3of the Bistable multivibrator (flip-flop) Q2,Q3 is turned "on"hard (saturated),so its collector voltage is very low,approaching zero voltsAt the same timeQ2is "cut off", so its collector voltage is very high,approximately at the positive supply voltage.,Q3collector is connected toQ4base via D4 & R13,&Q4is "cut off"so the relay is not operated.If the Bistable M/V changes state,Q2is now "saturated",&Q3is cutoff.Q3'scollector goes high.turningQ4"on",& operating the relay.So far,so good!How do we make the Bistable M/V change state?The mic "hears" the "clap" generating an ac signal at the base ofQ1.The amplified signal fromQ1is then fed to Q2,Q3,bases via C3,D2,& C4 ,D3.The diodes only pass the negative half cycle of the signal,presenting the bases with negative pulseswhich momentarily overcome the existing positive bias on the "saturated" transistor,(in this case,Q3) & turn it "off".Q3'scollector goes "high",biasingQ2"on".PS: I wouldn't panic much ,as far as the transistor types for the Bistable & relay driver are concerned,but Q1 is an amplifier.If it has insufficient voltage gain,its output may not be sufficient to trigger the Bistable into changing state.Another point is to get a mic which has a fairly high output voltage.Apparently they used an Electret mic,as they have an FET preamp built in,hence.R1.

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 04:08:43 am
content: Quote from: kizzap on March 06, 2014, 04:01:36 amhow do i go about calculating the biasing of the transistorsQuote from: vk6zgo on March 06, 2014, 04:03:02 ami know how the circuit works thanks for the explaination it helpedthe problem is getting it to work

author: vk6zgo
author_rank: Super Contributor
timestamp: March 06, 2014, 04:31:06 am
content: Sometimes it helps to trouble shoot the problem if you revise the operating principles.You could maybe,insert a negative voltage at the junction of C3,C4 & see if your Bistable changes state.What state is the Bistable in when you first turn it on?What state is Q4?You can see if Q4 turns on & off by connecting its base to + supply via a 5k or so resistor.Try placing your finger on the base of Q1.--------Induced Mains hum may be enough to trigger the Bistable.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 06, 2014, 05:16:43 am
content: There are some tips on biasing,etc on this site:http://www.rason.org/Projects/bipolamp/bipolamp.htmAnother place to look is the E-Book at All about Circuits.

author: AndyC_772
author_rank: Super Contributor
timestamp: March 06, 2014, 06:40:06 am
content: Quote from: electronics technician on March 06, 2014, 01:23:51 amTo get this sorted, you're going to have a very long, careful and methodical troubleshooting session. Make some coffee, you'll be needing it.Type the part numbers for the transistors you have into Google, find the data sheets, and check the pinouts. There is no short cut or substitute for this. Assume nothing.If you can, remove the transistors from your board and replace them with brand new ones, correctly connected. This will help ensure you're not wasting time trying to build a circuit with parts which have been damaged by incorrect use.Go round your circuit with a multimeter, and check what voltage exists at every point.EVERY point.When you have that information, post up a clearly annotated schematic, and maybe someone will be able to give you some pointers as to where faults exist, or some further experiments to try. A detailed, methodical analysis will look good in your report even if the circuit never works, so this is anything but wasted effort even if nobody replies at all.Post a photo of your board. Make sure it's clear, sharp, and has good lighting.Without a crystal clear picture of what your board looks like and what voltages exist where, it's impossible to debug it remotely.

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 03:04:55 pm
content: Quote from: vk6zgo on March 06, 2014, 05:16:43 amthanks i will check it outQuote from: AndyC_772 on March 06, 2014, 06:40:06 ami will post the pictures asap thanks for the advice

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 05:41:16 pm
content: are the transistors supposed to work as cbe and ebc or just ebc with flat spot facing you2n3904 npn transistors

author: Rerouter
author_rank: Super Contributor
timestamp: March 06, 2014, 07:58:23 pm
content: The transistor will only work in the pinout on the datasheet, and you can blow up most transistors if you feed more than 5V across the emitter to the base, (reversed polarity on NPN)with it facing you, wire it up as per this imagehttp://www.electronicecircuits.com/wp-content/uploads/2010/03/2N3904-NPN-General-Purpose-Amplifier.jpgAnd as per the first page of this thread, take some good images and we may be able to spot something obvious (just probably label the designators on the image in paint to make it easier to trace out)

author: electronics technician
author_rank: Regular Contributor
timestamp: March 06, 2014, 09:11:12 pm
content: i wired it exactly like that but i think the transistors itself are the problem i triple checked the circuit for wiring errors which i dont make often but when i powered it up the relay was clicking but not when i clapped so i will get more transistors and give and updateon how it went

author: electronics technician
author_rank: Regular Contributor
timestamp: March 18, 2014, 10:23:46 pm
content: i got it working the transistor Q2,3,4 were bad they were shorting across all pins thanks for all the help