Postbag: #38 - MPR121 Touch Sensor, 3.3v/5v Level Converters

[@bigclivedotcom]

Ah, you're way ahead of me. I've still got the APA strip sitting in my ebay shopping basket. I've never tried deliberately blowing a 1N4148 diode. I wonder if they might actually go short-circuit like their big brothers often do.

[@JulianIlett]

bigclivedotcom The strip I showed was an auction win. It's 60 leds/m and cost a lot less than another strip I bought that's just 30 leds/m. I'm going to try blowing ten diodes right now...

[@bigclivedotcom]

I just tested a 1N4148 with LOTS of current. It got very hot, smoked and then went short circuit. So you may have to make a SROM instead. (Snippable Read Only Memory)

[@TheChipmunk2008]

Yeah the behaviour of them when overloaded is 'undefined'. Maybe a 10 ohm 1/8watt resistor in series with each diode would be burnable to make a prom?

[@JulianIlett]

bigclivedotcom Hmm, the 1N4148 failure mode does appear to be 90% short circuit. The one test I did before ordering the bits for my PROM was an open circuit failure. There may be a problem! I might have to go with your SnipROM™ idea :)

[@bigclivedotcom]

Julian Ilett You could definitely make it work. But it would require a Photonicinduction approach and the programmer would probably be quite violent. (But it would make a great video if your mains incomer fuse lasted for the full programming session.)

[@edgeeffect]

Seeing that little "HOW IT WORKS" box on your screen took me right back to my youth! :)

[@jeffmorris2520]

Months ago when I was messing with NRF24L01s and ESP8266s I somehow ordered 100 of those AMS1117 boards. Don't know what I was thinking, but in the end it wasn't much money and they're excellent little units. No problems. I soldered pins into a dozen of them and I'm going to have to do a dozen more as they end up in breadboard circuits that I've shelved until they pique my interest again.

[@FranLab]

Cool!

[@Brant92M]

@pete r: First of all, you need the tach output AND ground connected. I think what I would do is attach an interrupt to the pin that you have the tach connected to. Every time it fires (either every rotation or half-rotation, IIRC), your program will jump to your interrupt routine. What you can do is set up a timer; if you've not gone into the interrupt routine in so many seconds, declare a fault and set off the buzzer. Make sure to check your datasheets and see if the pulses coming out of the tach are long enough for the arduino to reliably trigger on, there is a lower limit. If the pulses are too short, you might be able to get by with adding a small capacitor to stretch out the pulses. Let me know if you need more help!

[@griftereck]

Since seeing your videos. Ive bought some items from far east sellers. only takes about 20 days to get to Scotland. I got a kit of a "hot" LM386 amp. That was hot when I got the voltage polarity wrong. Works ok now tho. Ive got some more parts in the post today. A 555 and 4017 with a lot of leds, kit. see if I can burn my fingers building that up. :)

[@TommyAventador]

Adafruit has a board that uses this IC that does basically the same thing. They have sketches for this ic too.

[@hdmalpas]

Just to let you know that the 5 meter reel of RGB Leds came which I told you about, Very impressive for Six pounds from Banggoods, a very impressive display, and that was with them still on the reel. The amount of control via the hand controller is quite vast, well worth a look.

[@Chriva]

Now that diode pROM is something I'm looking forward to! Nothing beats the magic smoke in the morning :D

[@ww321]

Must be nice getting packages ever few days. Except you need time to assemble everything.

[@elboa8]

Why not make a PCB for the ETI project Julian? The cover brought back fond memories. Thanks.

[@zupnikal]

The MOSFETs marked as "J1" are BSS138 n-ch ones. The circuit is most likely something very similar to this: www.nxp.com/documents/application_note/an97055.pdf

[@JulianIlett]

***** Yes, I was sure I'd seen this circuit with MOSFETs. So the marking must be J1 - the rotated Y must mean something else. Super confusing!

[@superdau]

***** Wow, people can write quite alot about such a simple circuit. Do you prefer them in red? www.sparkfun.com/products/12009 ;) learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide It only works with MOSFETs btw. because the circuit needs the substrate-diode of the MOSFET.

[@tobortine]

Some very cool stuff. Alice should put you on commission given the advertising you do for her ;-)

[@JulianIlett]

tobortine Yeah, I wish I was on commission! I keep going back to Alice because she's always within a couple of pence (cents) of the cheapest eBay sellers, has all the latest stuff and has a pretty good feedback rating too.

[@tobortine]

Julian Ilett Indeed, I've bought things from her myself after watching your videos.

[@VaupellGaming]

Julian Ilett Alice is also one of my favorite sellers on Ebay, never had any problems. :D

[@XerotoLabs]

Julian Ilett yeah one of my fave sellers , was even happier when I found you channel , and saw you using that shop too.

[@Madmax23419]

***** Last year it is not as good as it was, couple of package not received and they let me wait and wait some more, after 10 mails over 3 moths later a give up. I no longer buy stuff from alice.

[@philluxsuisse]

OpAmps and other ESD-stuff packaged with this cheap chinese foam!!! Hope for you it's not damaged.

[@TheChipmunk2008]

Yes, in the UK drilling coins is legal, if frowned upon :)

I had reasonably good experience with atxmega32e5 for capacitive touch input. CY8CMBR2044 ain't bad as well, if you would like to omit programming uC.

[@Ogma3bandcamp]

Hi Julian, could you use washers instead of drilling coins? My 3.3V converters just arrived yesterday also. Got to stock up on some op-amps at that price. Great to hear Fran get a mention, I'm a big Franfan too. Thanks, as always.

[@JulianIlett]

***** Just found some coins with holes already in them - Korean I think - result :)

[@Mixbag]

im tying to use an arduino to set a buzzer off when a fan stops spinning. can anyone help me out a bit ? the only wire connected to the arduino is the tacho *yellow) cable from a 12v pc fan.

[@chrissouers8576]

Ha. I knew it came from Alice just from the description. Funny stuff.

[@Strawberrymaker]

my second liked electronics channel after eev. subscribed :)

[@JulianIlett]

***** Thanks, much appreciated

[@cyberlightbeing]

What's the average delivery time from Alice then?

[@Dosbomber]

Having used both, do you prefer to use the protoboards with interconnected pads (I think you're calling that stripboard), or the pad-per-hole protoboards? I've been using a lot of the interconnected variety lately (certainly less hassle than making my own PCBs for quick projects), and don't really like the idea of the pad-per-hole type. It just seems like unnecessary extra soldering and effort to make connections. I'm curious if you have any preference or thoughts on the comparison.

[@Brant92M]

Well, the tradeoff is that you have to cut the tracks on the stripboard. I like pad-per-hole better for that reason, I think it's easier to add extra wire or solder than it is to dull my knife on the fiberglass.

[@JulianIlett]

Brant Martin I agree, cutting stripboard tracks is a real pain - those track cutter tools are never sharp. I really enjoyed working with the pad-per-hole board

[@Dosbomber]

I use a Dremel to cut the traces. I don't think I've seen a special tool specifically for trace cutting.

[@Anvilshock]

What ever happened of your diode PROM?

[@AnorNeto]

oh really cool! you got the MPR121 I talked about :D

[@jusb1066]

what is your loss rate from China of late? mine is up to around 1in5 items dont arrive and have to get refunded

[@JulianIlett]

jusb1066 I've not lost anything recently - a couple of items went missing last year as I recall

[@zelra891]

It seems that Julian is using EMS. and what I can tell you is that we never choose this way while online shopping in China.

[@jusb1066]

EMS ?

[@TheHunChem]

When I saw all of the items scattered around the table, the first thing that came to my mind was that you just spent a fortune on that, but these components are suprisingly cheap...

[@KX36]

The TL072 look a bit fake to me. There are lots of fake components from china on ebay, especially common ICs. They usually still work but might for example be a different cheaper opamp with completely different specs. You should really get such things from RS or Farnell. Farnell is a bit more expensive than RS but free next day delivery over £20 (but it's awful UPS). RS is £5 next day delivery by parcel force or free collection at the trade counter with no minimum order.

[@AndrewBryantPianoTuner]

julian!!! There 13 Semitones in an Octave !!!!! Or 8 Tones.

[@JulianIlett]

Andrew Bryant pianotunerbristol That's a 'panels and posts' argument - I'm not getting into that one ツ

[@nozynoz]

great vid

[@stupidystu]

I believe pre 1969 coins are fine to destroy Julian. "The Coinage Act 1971 Section 10 (1)No person shall, except under the authority of a licence granted by the Treasury, melt down or break up any metal coin which is for the time being current in the United Kingdom or which, having been current there, has at any time after 16th May 1969 ceased to be so."

[@AndersJackson]

Think Norway have coins with holes in them already made. :-)

[@vickytuite8261]

Use Canadian pennies. They were discontinued in 2012.

[@marssheep1264]

Alice is a cheater, I ordered 3 items, never got them, then she said she will send them again with my next order so I made another order and guess what, it did not arrive, again. Save your money, do not buy from that shop.

[@GigotDagnot]

I bought a lot of items from Alice (thanks Julian for that). and they have always arrived here in France.

[@david_pilling]

I ordered one expensive item from Alice, it didn't come, and I had difficulty getting anyone to listen to me. Eventually they said they'd send a replacement which did not turn up. A few weeks later an irreplaceable package from a completely trustworthy local sender vanished. Conclusion one has to accept some losses from all sources. You can't argue with the feedback scores on ebay. Dumping the people with unreliable postal delivery may even be a good strategy for suppliers. When I see something I want I'll give Alice another go.

[@david_pilling]

David Pilling Replying to my own comment. I did gave Alice another try, the parts came in 11 days all nicely packaged. A good thing about Alice is that they sell so much electronics, unlike many other vendors on ebay one could get everything for a project from one source.

[@marssheep1264]

I was not that lucky, a week ago she promised refund, she sent me this message: "I just submitted the refund request. There should be results in 48 hrs. Thanks - alice1101983" today I informed her that I did not receive any refund and here is hers reply: "Oops. The refund was expired. I have to apply refund from another chanel. Is it possible for you to revise your feedback? If yes, it’s might be a strong support for me to apply the refund for you. Best regards, - alice1101983" not sending the goods AND blackmailing customers, nice way to run the bussines...

[@joeambly6807]

Read the ebay policies and get a refund....you didnt do it the proper way