Simple IR rotation speed sensor with TCRT5000L - Page 1
Forum section: electronics / projects

author: Redcat
author_rank: Regular Contributor
timestamp: August 24, 2015, 05:14:30 pm
content: It's been a while since I've posted my last project.I just wanted to share a nice little project i have done recently for our company.Nice beginner project and it might be interesting for someone who wants to use the TCRT5000L sensor.We have a very old RA4 photo paper developing machine in our lab (from the early 80s...) . It's doing it's job fine, but the corrosive chemical vapors are not that good for the electronic boards in the back of the machine and they get heavily corroded over time.As you can imagine, they stop working...This time it was the infrared rotation speed sensor board which is needed to get the run speed of the machine and so adjust the replenishing rate of the chemistry (i won't go into detail...).Here some photos of the old PCB and my new prototype board. This type of simple circuit is also sometimes used in robotics too for line detection or object detection, so it might be interesting for you.As you can see, the traces of the old board are almost gone...I have ordered some blue plastic spray (will arrive in the next days i hope) and will cover the new boards (there are 2 identical in the machine) completely in plastic to protect them. We will see how it works out.The chinese 4x6cm mini PCBs i had laying around came in very handy. Not as nice as an etched PCB, but i'm very limeded in repair budget and it works.I have done 3 new pads with some cut out metal and the original pads at the PCB edge i have removed with a hot soldering iron. Just 3 Pads are used. Even on the old circuit (there seems to be much stuff on it which is not used...i don't care). Connections are from top down: +15V, -slit- , Ground, Signal out (0V/15V).Here is the new board installed:As you can see, the sensor is looking on a black plastic wheel with white stripes like this:.This way the rotation speed is measured. The sensor puts out a rectangle wave. When he sees a white stripe, the output changes. The analysis of the signals is done in another logic circuit.Here is the schematic of this simple circuit. You can easily make it work for lower Voltages(like 5V or so) by just changing the resistor value for the IR LED:(I had to photoshop out all the part numbers, because they differ from my schematic... i'm not so familar with the fritzing pcb software... but this is how the layout for the 4x6cm pcb looks like.)Yes, right angles everywhere, it's a proto board.It uses the TCRT5000L IR proximity sensor for detection. An LM 358 OpAmp is used as comparator and the detection level is adjusted with the 10K trimmer.Works quite nice, it can differenciate between black and white areas. But distance is limited to under 2cm. With a bigger IR LED/phototransistor combination you can reach a higher distance, but i was happy to get at least a TCRT5000L (a combined IR LED+phototransistor sensor)....Have fun with this nice beginner project.

author: tautech
author_rank: Super Contributor
timestamp: August 24, 2015, 08:47:29 pm
content: Thanks for sharing.For PCB prtection I use this Lacquer spray:http://www.jaycar.co.nz/Service-Aids/Chemical-Aids/Aerosols/Circuit-Board-Lacquer-Spray-Can/p/NA1002

author: Redcat
author_rank: Regular Contributor
timestamp: August 28, 2015, 04:43:44 pm
content: Thanks tautech for your reply.My protection spray arrived and I just covered the whole PCB in blue gunk...Tesafilm on the IR sensor and trimmer of course.It says it is acid resistive which is ok - we have a mix of acid and basic vapors...we will see how long it survives.The Name is "Teslanol T7".It's also usable for transformer isolation and winding protection.Here are some photos:I thought it would be much thicker (I would have prefered)...it is very thin. If it doesn't work, i probably dip the whole thing into liquid rubber.I have read the short description of your spray and it sounds good too, but I took what was available.Nice greetings

author: eneuro
author_rank: Super Contributor
timestamp: August 29, 2015, 02:13:39 am
content: Quote from: tautech on August 24, 2015, 08:47:29 pmI'd start rather with waterproof marker, painted those few tracks od double layer copper small plate, then etched in solution and within less than 1 hour one can have something which looks like electronics PCB, but those bloody prototype PCBs which can be usefull to quickly test something, but insert this thing as pernament solution?It looks so crappy as it is - sorry, you must be very lazy if you didn't made even hand painted PCB

author: Redcat
author_rank: Regular Contributor
timestamp: August 29, 2015, 07:18:48 pm
content: Hahaha..you don't know...Yes I would propably also make a nice PCB, but nobody wants to pay for it...My boss can be happy that I made this like it is. He can have this for almost no money or he can have nothing...Do you understand now? You can make it better if you like.I'm a tech who can (has to) make something out of nothing, every and every day. So your coment doesn't bother meI just wanted to show the project.

author: retrolefty
author_rank: Super Contributor
timestamp: August 30, 2015, 02:03:06 pm
content: Quote from: Redcat on August 29, 2015, 07:18:48 pmGood for you.A good tech's goal is to keep them up and running no matter the difficulties the real world throws your way.

author: eneuro
author_rank: Super Contributor
timestamp: August 30, 2015, 05:15:52 pm
content: Quote from: Redcat on August 29, 2015, 07:18:48 pmHumans do beautifull things not only for money... but beacause of it is in their nature...You didn't showed this spirit in this project and didn't made such effort

author: Redcat
author_rank: Regular Contributor
timestamp: August 30, 2015, 09:10:02 pm
content: @retroleftyThank you retrolefty for your nice comment.@eneuroTruth is, i'm not really an educated tech. I had to learn all myself.My job is photo media, i'm not payed for technical stuff. But there is no tech guy in the company.No one who has a good technical understanding and has ideas to do things with the simplest materials to keep things running.My best friend is into metal works and can build for me mechanical stuff and i know engeneers who can help me with technical questions to execute my ideas.Often you simply can't get parts anymore and/or they are so expensive that you could place a big chunk of gold in place.This sensor project is some dust in a desert compared to things i have done in the past. Electronics, Software, mechanical stuff...all you can think of.Sometimes i have to fight one year to get a new part...thats not fun. Thats not my job, but noone else cares.Funny story last week: I said to my boss "we need a new sensor" (again an IR sensor - seems they die fast, but for a modern printing press...so no DIY project) and he answered to me"What should I do now?" and i answered "What shouldIdo now?". No new one was bought. Machine will fail pretty soon, but then I don't care. Really.Nobody who can solve technical problems there and in my time at the company i have invested hundreds of hours of my freetime...for free.Investigating problems and learn, google the hell out of the internet and building or programming stuff. (Ok, i have learned a lot and thats a good thing.)Not to mention the time which i loose from my actual worktime.It's not everytime fun when you have your desk full of work and every 5 minutes someone comes to you with a problem... (sometimes it's ok to see something diiferent and free the head).I have a lot of other things to do. Not tech stuff.Saved them thousands of Euros in the last years, by using my brain and connections...for free. Not to mention the technical equipment that i bought...from my money.I'm really not always right. But most of the time.And by the way..i'm in the process of building 2 more boards...Muahaha.Some day i might get lasered PCBs...(connections..you know). Until then I love my proto boards from China.So yes, I simply show the spirit by doing it. That's more than you can expect for free.I like doing this and i like my company, or i wouldn't do it.I hope we can end this here, have fun.

author: Isad
author_rank: Frequent Contributor
timestamp: August 30, 2015, 09:52:38 pm
content: Quote from: Redcat on August 30, 2015, 09:10:02 pmThis was my life in a nutshell couple of years ago until i decided to goall for electronics.Thnaks for the circuit it might be easy but you just came up withthis the moment i needed it .Keep doing what you doing and keep your head straight.

author: Redcat
author_rank: Regular Contributor
timestamp: August 30, 2015, 11:02:14 pm
content: Thanks alot @Isadfor the nice words.My head is straight and will always be.

author: Asim
author_rank: Regular Contributor
timestamp: August 31, 2015, 08:22:47 am
content: Good job redcat. I wonder why some people are always hating !!

author: alsetalokin4017
author_rank: Super Contributor
timestamp: August 31, 2015, 09:02:04 am
content: Well... perhaps I should leave this one alone, but... personally, I detest that "pad-per-hole" stuff for actual circuitry. Once the simple circuit is breadboarded and working, it is very easy, as eneuro has said, to layout and etch a simple PCB for the finished project using ordinary Sharpie-style marker pen and ferric chloride solution. This is, in my opinion, actually easier than using the pad-per-hole boards, since once the PCB is etched all you need to do is install and solder the through-hole components. I sometimes find it easier to drill the holes first according to the template, then "connect the dots" with the Sharpie marker, then etch.I don't see any reason to be all nasty about it though; ultimately, what works works. Of course if one really doesn't want to spend any new money and one has the pad-per-hole stuff on hand, that's one thing, but spending 20 dollars US on a bottle of Ferric Chloride, a marker pen, and a piece of blank PCB will allow one to make a good handful of small PCBs and ultimately save time, which is the most expensive commodity after all.Congratulations, Redcat, on keeping your equipment running, however you choose to do it!(There are plenty of easy tutorials on YouTube on making simple and complex PCBs at home. I've even posted one myself, pitched at the usual "eighth grade" level.)

author: BillyD
author_rank: Regular Contributor
timestamp: August 31, 2015, 09:05:07 am
content: Good job, well done.