EEVblog #267 - Voltage Detection Stick Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: April 11, 2012, 08:05:59 am
content: I did a quick check on the main IC, and it's showing pin 4 is ground and pin 11 is Vcc. Hmm...Dave.

author: T4P
author_rank: Super Contributor
timestamp: April 11, 2012, 11:15:12 am
content: Custom Logic maybe ?

author: firewalker
author_rank: Super Contributor
timestamp: April 11, 2012, 11:17:17 am
content: Was the audio really bad on this episode or it was just my idea?Alexander.

author: david77
author_rank: Frequent Contributor
timestamp: April 11, 2012, 11:19:54 am
content: Could it maybe be an opamp, LM324 or similar? They have power on 4 & 11.

author: EEVblog
author_rank: Unknown
timestamp: April 11, 2012, 11:23:14 am
content: Quote from: firewalker on April 11, 2012, 11:17:17 amYes, the in front of camera audio is crap.I need to fix this, my shotgun just picks up too much crap in the new lab.Dave.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: April 11, 2012, 01:40:44 pm
content: Hi DaveDo you find these voltage sticks useful? More of a novelty in my opinion but what do others think?

author: IanB
author_rank: Super Contributor
timestamp: April 11, 2012, 03:38:40 pm
content: Quote from: FreeThinker on April 11, 2012, 01:40:44 pmI've been using mine a lot lately when replacing electric sockets. It's really handy to check which wires and outlets are live when a breaker is tripped and which ones are off. Much quicker just to touch the detector to a wire than to mess around with meter probes.

author: sacherjj
author_rank: Frequent Contributor
timestamp: April 11, 2012, 04:32:13 pm
content: Quote from: EEVblog on April 11, 2012, 11:23:14 amWireless lapel mic?

author: Rufus
author_rank: Super Contributor
timestamp: April 11, 2012, 04:33:55 pm
content: Quote from: EEVblog on April 11, 2012, 08:05:59 amProbably a quad CMOS op-amp then.

author: saturation
author_rank: Super Contributor
timestamp: April 11, 2012, 06:42:54 pm
content: Its very helpful doing electrical work. When you see wires, even if you powered down the circuit breakers for whatever you're working on, you case easily find the live wire.Quote from: FreeThinker on April 11, 2012, 01:40:44 pm

author: FreeThinker
author_rank: Frequent Contributor
timestamp: April 11, 2012, 07:46:46 pm
content: I've found them either way too sensitive (ie you cannot trace individual wires) or very erratic and failing to light up (similar wires out of phase cancelling each other out?) Never liked or trusted them, prefer a contact probe, a little more hassle but very reliable. Not a lot of price difference between the two but a world of difference in function/reliability.

author: SeanB
author_rank: Super Contributor
timestamp: April 11, 2012, 07:56:41 pm
content: I still like contact probes, I have 2. A cheap Steinel that uses neons and a VDR to drive the LED's, and an old moving iron unit that does double duty as a voltage tester and voltmeter/ earth leakage tester ( if I press the button while one lead is on grounded metal) with ultra sharp steel probes.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 12, 2012, 01:18:21 am
content: My volt stick is probably one of my favourite tools. But really only useful for mains powered circuits.Great for tracing domestic/building mains circuits back to the switchboard.I asked a sparky once whether he trusted them, he said he trusts it when it's glowing.I bought a Fluke one, I have never known it to not detect if a circuit is live.

author: david77
author_rank: Frequent Contributor
timestamp: April 12, 2012, 06:37:30 am
content: I've tried several volt sticks, all different brands and haven't found one that I could fully trust. Sometimes they are over sensitive and react 10cm away from a live wire, sometimes you stick them into the live side of a socket and they do not light up.That's rubbish. These things are unneccesary and can sometimes be dangerous, making you believe a wire is not live until you touch it and learn your lesson. I'd lump them into the toy section together with the screwdrivers with neon indicators.The only way to determine what's live and what's not is to use a meter or better still something designed for the job, like this:http://www.conrad.de/medias/global/ce/1000_1999/1200/1250/1253/125379_BB_00_FB.EPS_1000.jpg.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 12, 2012, 11:13:25 am
content: Hi david77I think your right, don't use them if you don't trust them.I am not sure if you understood the full meaning of what I saidQuoteThat means he trusts it when the volt stick is saying it is dangerous, but doesn't trust it when it is saying it is not dangerous.As for me, I trust it to read the efield strength between its antenna and its ground. If you are working in an area with a lot of stray efields, such as in a switchboard, then you should be using your multimeter, if you are somewhere else in the building, trying to figure out what circuit a particular wire or mains outlet is on, it is just so much quicker.

author: hlavac
author_rank: Frequent Contributor
timestamp: April 13, 2012, 12:35:59 am
content: Dave, I have better explanation of the patented frontend circuit discussed in the video.The cap and resistor between B and C together with the next inverter and its input protection diodes act as a pulse shortener.It sends a short pulse out every time the input transitions from low to high.If the input is stuck on either logic level there will be no pulses going out.These pulses charge the second cap thru the diode while the resistor in parallel with it discharges it.This means that the cap voltage will rise over the logic high level threshold if there are enough pulses in a time span to charge the cap more than it is discharged by the resistor.So output of the inverter behind the second cap will signal continous presence of series of low to high transitions on the input, that is the AC signal capacitively coupled onto the probe tip.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: April 13, 2012, 06:13:40 am
content: Yes it sounds right. This is almost exactly what circuit description section in patent say (lines 15 to 20, left column). I understand that the output will look like smoothed-out DC , almost like from switching DC-DC converter.

author: eV1Te
author_rank: Regular Contributor
timestamp: April 15, 2012, 01:27:46 pm
content: It would be interesting to compare the circuit design in the Fluke voltalert to the patent and the one that Dave tested now. Maybe Fluke hasn't scraped the labels of their ICs

author: elCap
author_rank: Regular Contributor
timestamp: April 16, 2012, 09:04:33 am
content: I have a volt stick from Tequipment.net (their own brand) which is totally useless. Do not buy it!! Its red LED turns on when there is no voltage, and off when close to a voltage source. But sometimes opposite. Having it close to an earth connection lights up the LED.Printed on it is the same patent number as on the one Dave did the teardown of. I will do a destructive teardown of it to see if it's same design.I have to buy a Fluke which I was aiming for in the first place (Tequ. cannot send Fluke items abroad).

author: IanB
author_rank: Super Contributor
timestamp: April 16, 2012, 03:04:59 pm
content: I have volt sticks from Fluke and Klein Tools. Both of them work equally effectively at telling live wires from unenergized wires. On a two core cable they can tell the live conductor from the neutral conductor by touching to one side of the cable or the other. They are helpful in tracing a particular cable in a cable run where I want to know which cable is live or not. When I use them on mains wiring I get neither false positives nor false negatives. Performance may vary but I have no problem with the performance of these items. If it lights up and beeps when I touch a mains conductor, that conductor is live, no question.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: April 16, 2012, 03:14:27 pm
content: Quote from: IanB on April 16, 2012, 03:04:59 pmUnfortunately WHEN it doesn't light up on a live conductor are when the problems start.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: April 16, 2012, 03:22:13 pm
content: Quote from: FreeThinker on April 16, 2012, 03:14:27 pmI'd say it would be the end to all your problems.

author: IanB
author_rank: Super Contributor
timestamp: April 16, 2012, 05:03:43 pm
content: Quote from: FreeThinker on April 16, 2012, 03:14:27 pmI've tested it a lot and that's never happened. So far my confidence is sustained.

author: saturation
author_rank: Super Contributor
timestamp: April 16, 2012, 08:03:31 pm
content: Same here. Many of them boot with built in self check, part of their firmware. If you touch it it will chirp and is quick user based self check. Lastly, you can check its response to a known live wire as tested by your DMM, before you go hunting among cables of unknown state.Quote from: IanB on April 16, 2012, 05:03:43 pm

author: FreeThinker
author_rank: Frequent Contributor
timestamp: April 16, 2012, 08:22:23 pm
content: Quote from: IanB on April 16, 2012, 05:03:43 pmAnd how many times would it take for a failure to 'shock' you out of your confidence?Ok Voltage sticks do work, but the whole concept of them is fundamentally flawed as a safety check and as a fault finder leave a lot to be desired. If you must use one use it with care, if you have an alternative method use that in preference. Not to mention the variability of these things, the one Dave stripped down was of OK construction as I am sure is the Fluke but believe me the one hung low brigade are not so particular and these are 'Badge engineered' by some of the big names so just take care

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 16, 2012, 11:27:25 pm
content: QuoteI am not really sure what is fundamentally flawed, from what I can see it is just detecting a time varying electric field. Which is actually similar in principal to a multimeter.As a fault finder it is great in circumstances where you are tracing cables and you dont want to cut them or open a junction box to see if they are on a particular circuit.In those cases it probably would be more risky to not use a volt stick.Other safety issues with the multimeter method of testing for a live circuit are having your leads plugged wrongly and causing a short, having your leads not fully in and not realising it, having damaged leads but not knowing and maybe on some meters having the meter switched to DC instead of AC volts.Also if you think that build construction is an issue then you need to think that build construction is an issue for any test equipment, especially test equipment that is making direct contact with live wires.I think it is a great tool, mine is a fluke mark II, but I only use in certain situations, and as I was told once "You can trust itifit is glowing".

author: elCap
author_rank: Regular Contributor
timestamp: April 17, 2012, 05:53:36 am
content: Pictures of Tequpiment volt stick, in action and teardown. Not many parts in it. It follows the patent seen in Dave's teardown, but with a few components taken away.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 18, 2012, 11:45:03 am
content: elCap, I think you're being a little disingenuous.I think if you are trying to point out a weakness in this type of equipment you should state a few more details of what you think could have caused the false readings, in these particular snaps.Maybe even do it again with a video camera hold the stick in your hand and wave it around. ie normal mode of operation.or Sorry I could be wrong, your volt stick just doesn't work.

author: Spawn
author_rank: Frequent Contributor
timestamp: April 18, 2012, 07:30:00 pm
content: I lost my very old Fluke Voltalert while ago, after seeing Dave’s video I remember to get another one, I received it today and I must say upgrading to newer version equipment is not bad idea after al. The new one is working a lot better than my old Fluke Voltalert.I didn’t get a Fluke now but German made Testboy 110 (funny name if you ask me) with a torchlight at the end, it is picking up a lot better than my old Fluke, I am sure the new versions of Fluke work good too.

author: elCap
author_rank: Regular Contributor
timestamp: April 19, 2012, 01:41:04 am
content: Yes, you are right. It was just an example of when I get wrong readings. I don't have a video camera so I just snapped a few photos. I cannot trust it at all where I'm using it (at home, at my bench). And I have no idea why I get wrong readings. Maybe the electric environment at my bench is the problem?I will buy another brand to see if it works better for me.Quote from: HackedFridgeMagnet on April 18, 2012, 11:45:03 am

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 19, 2012, 03:08:24 am
content: I have a fluke that is mark II or something.Not sure what mains voltage is like in your country but it only just occurred to me that these things would work a lot better where there is 230 volts than where there is 110volts. We use 230 volts, and where I live it is normally close to 250v. That is probably why the readings I get off it are so reliable.the Fluke stick also has a pair of leds, one is blue and nominally about 90 volts I think and the other is red meaning danger mains voltage.As you approach mains you will get first blue then red, but the blue led gives you a bit of a feel for what other efields might be present, such as data and stuff that could effect your readings. I must admit I get a lot of the blue flashes just from the ethernet and pstn and even large bits of metal.So I am thinking that that if you have a lot of stray fields in your room from data or whatever and your mains is only 110volts then your volt stick probably wouldn't be very reliable.