#433

[@parikshitsah12]

Thanks for making this. It's the best video I've found on TIAs

[@artunkopar9034]

Thank you sir. Your demonstration and clear explaination really helped me a lot for understanding the concept.

[@IMSAIGuy]

Glad to hear that

[@IceNein763]

One useful way to check to see if a remote control works is to use your cell phone camera. Most cellphone camera's CCDs don't fully block IR, so it will show up as a dim blue light through the camera.

[@DaveRChallis]

Nice video! I always enjoy your posts. One note: at roughly 16:00 you show the diode current backwards. The currents don't "cancel". By KCL, the sum of the currents entering then node equal the sum leaving the node (Opamp bias currents being ignored). The photo current through the diode is a reverse bias current, cathode to anode. So the current will flow from the opamp output, through the resistor, to the inverting node, then through the diode to ground.

[@IMSAIGuy]

your are right. was thinking voltage

[@Enigma758]

@@IMSAIGuy But I do think you were correct in that the feedback current matches the photodiode current and sum to zero as per KCL. It just means that since those two branches cancel, the current for the third branch leading to the op amps input must be zero. So in some sense, because the two branches "cancel", the third branch must be zero.

[@sathindranidhiyarasu1066]

Thank you for making this video. It was of immense help.

[@HarleyKing001]

Thank you for your video. I enjoyed the discussion of the transimpedance amplifier. Thank you for the schematic discussion.

[@IMSAIGuy]

Glad you enjoyed it!

[@byronwatkins2565]

First, lines on log-log plots are power laws, y=ax^b; linear is the special case b=1. Second, at room intensity the current is nA. To make a light level meter, for example, use a current divider in the feedback path to get an equivalent feedback resistance in the 100 MOhm range. Third, for faster response you need to reverse bias the diode a few volts rather than 0 V; this trades linearity for speed. To get faster still, you must use smaller diodes with less C and diodes optimized for speed. LEDs actually make decent fast photodiodes when reverse biased a couple of volts.

[@FF7824]

Really well done explanation and interesting project. Thanks.

[@IMSAIGuy]

thank you

[@mwerensteijn]

Super helpful video! Thank you for the clear explanation and demonstration!

[@aduedc]

Good job. I think Opamps are slow , good for remote control; however, I put photo diode directly to Base of NPN transistor for faster response.

[@ivolol]

You omitted the capacitor in the built circuit? Looks a lot like a pico/nanoammeter circuit :D

[@maheshmagalage1886]

Thank you for the video. Really helpful. I wonder if the output can be used as a line-in input to an audio amp?

[@michaelhompus2475]

Interesting video but I did see something I do not understand. At around 16:00 you show a 1 µA photocurrent going into the node connected to the neg-input of the opamp. Also the 1 µA current trough the resistor is flowing into that same node. According to Kirchhoff's law the sum of currrents in a node is zero. The input resistance of the op-amp is too high to drain the sum of both currents, so the only remaining path for the photocurrent is via the resistor, 'upward' in the diagram. Thus the current direction in the resistor is opposite of what you have drawn. For a current to flow in that direction, considering the neg-input of the op-amp being 0V, the voltage (+V) must be negative according to Ohm's law.... OK, the op-amp will take care of that. But, at 18:40 you say that the LED will light up if the photo-diode is illuminated. According to your diagram the LED will light up when the output voltage of the op-amp is positive.... Did I miss some theory here or is your physical circuit different from the diagram? Reversing the photodiode f.i. will make the output of the op-amp positive when the PD is illuminated. What op-amp did you use? It must be rail-to-rail (and a bit more) on the inputs for this circuit to work with a single supply.

[@Neverforget71324]

15:39 Mr. Kirchhoff... we have a problem.

[@TheDerpsFinest]

Very interesting. What’s a big way you learned all of this info? Books? School? Internet?

[@IMSAIGuy]

School: Math and Physics degrees Ham Radio Books: kzbin.info/www/bejne/hXOxnWBso6usgpI Work tinkering

[@fanlin9111]

Very useful and thanks for sharing! One questing here, I heard that to get faster response we need to put a inverse voltage to the PD. So what’s the response time of this design you have? Can I use this for the IR signal decoding?

[@IMSAIGuy]

It was not designed for speed but I'm sure it is fine for IR decoding which is quite slow.

[@Электроника1234]

Best explanation, now I can connect it

[@hullinstruments]

Had no idea you were in the optics stuff. It would be awesome if you did some optics and laser experiments on your channel! If you watch Les’s lab, he made a wonderful series on DIY TEA nitrogen lasers and pump dye lasers. Out of basically scraps and trash. I’m building my third iteration at the moment, measuring output and finding a fast rise time pyroelectric sensor was a really interesting part of that design, and I’m surprised I’m just now stumbling across your video. It’s been a lot of fun… I was into laser and optic stuff along time before getting into the pumped dye stuff. And became interested in it only because if Les’s videos. Took me years to put together a real optics lab in the corner of my electronics lab… Finding stuff like optical tables and equipment takes forever. No way in hell I could have afforded it at the prices they charge. But stalking eBay enough… And visit plenty of industrial, University, and government auctions in person… And you’ll end up with pallets of the stuff for pennies on the dollar! Would love to see more optical stuff from you. Thank you for your content!!

[@cinematoart1621]

Excellent work.

[@dwagner6]

Is that a Zebra Sarasa pen you’re using? I’m not a pen aficionado, but it’s the only ballpoint I actually like using.

[@IMSAIGuy]

best pen

[@giannissotiropoulos3721]

Great video. How could i connect this in an arduino so it can read the voltage? (analog input) thank you

[@dancollins1012]

Good video. Special request - include discussion of electrical bandwidth to support those folk doing Li-Fi / optical communications projects

[@IMSAIGuy]

I'll start with ship to ship. Morse code with lamp and louvers.

[@IMSAIGuy]

Seriously, I'm not the right person. my friend does hundreds of terrabits per second fiber stuff. It's not silicon!

[@moodeomaar]

Very useful. I just have few questions 1. What is the amplifier chip 2. You didnt show in the drawing where you connect the supply to the circuit Im still confused of where the supply should be connected to the circuit Thanks a lot

[@IMSAIGuy]

at 19:29 you can see it is a TLC272 opamp. the orange wires are power and ground. pin 8 Vcc pin 4 Gnd

[@moodeomaar]

@@IMSAIGuy Thanks a lot

[@RamanYadavRomy]

Thanks for sharing 👍

[@JonathanNagel]

Thanks for all the great videos. What photodiode is the closest to a PMT for very low light detection?

[@IMSAIGuy]

The PMT is very good for low light. A diode will never match it. If you want the best chance then you need a large diode. I've used the PIN-10D diode in a BNC mount. one square centimeter diode. About $100. You will need a very good amp. For low light you might also optical chop the light and use a lock-in amplifier. www.osioptoelectronics.com/application-notes/osi_parts_catalog.pdf

[@IMSAIGuy]

www.thorlabs.com/NewGroupPage9_PF.cfm?ObjectGroup_ID=287

[@IMSAIGuy]

www.thinksrs.com/products/sr810830.html

[@norbertme]

Hello there IMSAY Guy, I got a 13AMP003 also to help me out on a project building a TIA. Unfortunately it sometimes gibberishes the values and fluctuates a lot. Could you give some advice on repair ? Have been really enjoying your channel this year, cause this video led me here in May. Thank you for your work and keep it up. All the best !

[@IMSAIGuy]

I don't think you will find schematics. Those have an internal battery so you might remove/replace that

[@norbertme]

@@IMSAIGuy Thanks a lot, but it's not that. I'll try drawing the schematic and maybe changing some components. Best Regards .

[@norbertme]

@@IMSAIGuy Hello. Managed to repair it. It was the internal regulator which was faulty. Always check the voltages going in :) . On batteries it works fine.

[@steveberg3014]

Will a 741 op amp work in place of 272

[@IMSAIGuy]

yes, but with modification to the circuit. The 741 needs a +/- voltage supply

[@zerobow9413]

Nice job ! read 10 books and 100`s of circuits on ir-op-amps your vid beat em all !!!

[@IMSAIGuy]

Glad to hear

[@Enigma758]

I seem to find many references to photodiode circuits that simply use a voltage divider. I tried a similar experiment as yours using a photodiode (one that resembles a waterclear LED) to trigger a red LED. When I operate the room's dimmer, the LED tracks it very well. So perhaps a transimpedance amplifier is not always necessary. Here's one of several references: electronics.stackexchange.com/questions/33659/how-do-i-connect-a-photodiode

[@IMSAIGuy]

yup, and sometimes you can use a transistor instead of an opamp. just depends on what you need

[@Enigma758]

@@IMSAIGuy Perfect answer, thanks.

[@IMSAIGuy]

@@Enigma758 I'm used to photodiodes needing lots of gain. common to have 400M ohm resistor in the feedback for low signals. If you don't need any gain then something as simple as a resistor can work fine.

[@wegi9621]

Epic!

[@hariharankrishnan7189]

Dear Sir! I am from India. It's a nice and useful video. I have two doubts. 1. For a particular photodiode, how to practically calculate the minimum and maximum photocurrent, it can generate? 2. Can you tell the model no. of the 'Melles Griot' Large Dynamic Range Amplifier? I am looking for the purchase link.. -- Thanks in Advance!!!

[@IMSAIGuy]

1. 13AMP003 2. datasheet