Can I replace electrolytic caps with tantalum?

I'm thinking of replacing some electrolytic caps with smaller ones to save space. Foresee any problems? I was thinking tantalum just because they looked like they might be smaller. This is for a AAA 1.2-1.5V circuit.

Posted by royalestel 11 years ago


What to buy if your a beginner

Hello, I'm 13 and I want to get started in electronics. I know how to solder and read basic schematics and I have two of those 200 in 1 electronics sets. I am about to make an order for some components from www.bitsbox.co.uk.This is what I have so far, anything you would add or remove? (I couldn't easily get the quantities)pp3 battery clips2 x AA Battery Holder3 x AA Battery Holder11 wire single core bundle1uF 50V Electrolytic Radial100uF 25V Electrolytic Radial220uF 16V Electrolytic Radial22uF 50V Electrolytic Radial25-way PCB D-connector PlugPrototyping breadboard 80x60Watch crystal1N4001 Rectifier Diode 1A 50VStripboard 95x64White LED 5mm 30000mcd24V 16A SPST K4TA24 RelayPiezo Transducer with Flying Leads7805 voltage regulator (to get a steady 5v from a wall wart for the breadboard)NE555 timer IC2N3904 NPN transistorBC213 TransistorATTiny2313-20PUlm386 op-ampStandard Toggle SPSTupdates:I have a multimeter, resistors and LEDs and I am buildng an attiny 2313 programmer as well as adding to my collection.

Posted by josh92176 11 years ago


Electrolytic Capacitor Horizontal Footprint Eagle

I am designing a very simple but small PCB in Eagle. Size is a constraint and the enclosure is pretty small. I had a 100uF electrolytic capacitor in the schematic which I realized will not fit vertically in the enclosure while making the prototype. So to make it fit, I kept a few mm of leads between PCB and capacitor while soldering and then bent it horizontally on top of a nearby crystal. This was a quick fix but now I want the schematic to have space for it. I have enough free space to put it lying down but can't find any footprint for a horizontal radial polarized cap. I'm sure I saw one such component in some schematic or in the library but can't find it. Even google results mostly gave axial caps. The only thing near to what I wanted was this diagram, but it had no footprint. The last resort will be to design my own footprint. Can anyone please help? -Antzy

Posted by Antzy Carmasaic 5 years ago


Ker-Pow!-citor

So, my circuits professor described electrolytic capacitors today, and said that reverse-biasing them could cause a catastrophic, eye-popping explosion. All that in a little metal can? I had to try it! Here's what it takes:

Posted by stasterisk 10 years ago


i need more amps for my hho generator.......HELPPPPPPP

I've built a hho generator (the spiral electrodes kind) and am trying to use it as a welder i use salt as my electrolyte (should i use something else???) THE PROBLEM IS THAT WHILE I DO GET A CONSTANT FLAME, I DON'T GET A BIG ENOUGH FLAME (it melts metal but it takes ages to do so) does anyone know of a way how i could get more amps to speed up gas production or of any way i could get more preasure (+maybe my gas isn't pure enough because i use salt as an electrolyte, could that be it?)

Posted by CrtSuznik 8 years ago


Must have capacitors, resistors, transistors

I am wanting to know the best values/ most used values in electronics projects for resistors, capacitors, and transistors. Suggestions? Also when purchasing capacitors, ceramic vs. electrolyte? Are ceramic mostly for lower capacitance values? And lastly what is the difference between a 10k resistor and a 10 Ohm resistor. What I have figured out is that the 10k is a higher resistance value.  Thanks, diamondmine

Posted by diamondmine 4 years ago


HHO generator with iron electrodes

Hello Everyone, I recently found out about Sodium Hydroxide as an electrolyte. I have read that it does not affect the electrodes like salt or baking soda and it does not create any weird gasses like chlorine. The main reason for using stainless steel electrodes is to prevent this corrosion, but since sodium hydroxide does not create this corrosion, can I just use the much cheaper iron or regular steel as the electrode plates? Thanks in advance  

Posted by JStuyfzand 2 years ago


Make supercapacitors from graphite in a DVD burner

The outline is that you can deposit graphite oxide (a cheap bulk material) onto a film of PET (the plastic used in Coke bottles), hit it with a commodity infra-red laser (such as the one in a $30 LightScribe DVD burner) and end up with a form of activated carbon material that can be used as the electrode in an electrolytic capacitor.  Add some aluminium foil, separator membrane and electrolyte and you've got cheap, robust energy storage.  The headline numbers are a few hundred milliFarads per cubic centimetre at a few volts, which works out to 1.36kWh per cubic metre of stacked capacitors.  It's still about 50 times less energy per volume than lead acid batteries, but you could store as much energy as your house will need overnight in the size of a garden shed or a set of bunk beds.  They charge/discharge in seconds and retain >95% capacity at 10,000 cycles so seem suitable for storage to even out intermittent energy generation from, for example, solar or wind power. I'm really thinking about cost here- unless I'm missing something fundamental it doesn't seem like producing these on a high volume roll-to-roll process would be excessively difficult, and the cycle life means the replacement time would be many years even in heavy usage.  Could you get sufficient kWh per dollar to make these a viable storage mechanism for home-scale renewables? There's a more informative article here.

Posted by PKM 6 years ago


Repair of Electronic choke for 4'tube light

I tried to repair two electronic chokes for 4' fluorescent tubes but cdn't succeed. If any one kindly help me by providing a step by step guide with the test voltages etc. at important points in the circuit, I will be ever grateful. The following things have been already done/checked. Physical checking of any defect/damage/burning marks etc., DC voltage after rectification is OK, Filter capacitor (DC voltage  after rectification ) is checked OK, Other electrolytic capacitors chked to be OK, one of the 13005 transistors was found defective - changed with a new one, but no result. Voltages at the transistor terminals seem to be OK.. May pls write to me directly. B.N.Bhattacharya bnber_2004@yahoo.co.in

Posted by bnber3451 1 year ago


homebrew ultrasonic cleaning solutions

I just picked up a branson 5210 2.5 gallon ultrasonic cleaner.i will be using it to clean aluminum motorcycle carbs that have been sitting and become encrudded.i have gotten a lot of suggestions as to what sort of home brew recipes work well, i was hoping people around here could tell me what they use or have heardi will be ordering some of the carb cleaning stuff from sharperteks website to compare it to different homebrew recipes. my goal is ease and lack of cost here. thankshttp://i9.ebayimg.com/01/i/001/43/54/91b8_35.JPG

Posted by 666mph 9 years ago


Ignition Coil

Yes, I just posted something on a flyback. I was interested in that, until I saw this. It got me interested in ignition coils, so I got one new from the autoparts store for $20 (USD). I looked on the site, for the schematic, and realized that I didn't know what the rectangle was. Is it a resistor? I'm new to electronics, what size resistor do I need (if it even is a resistor)?What about the capacitor? I have a 100uf 200v electrolytic one, will that work?Also, part of the core is not in the coil, it's square shaped, could I rig it to work like this flyback circuit?Or this one? (simple driver circuit)?Sorry about the never ending beginner electronics questions, I just really don't have anyone else to ask.

Posted by John Smith 11 years ago


Help!! It's 3am and I have a bubbling and squeaking battery!

Please help! I procured an electric wheelchair today (worn and torn, but in good shape.  It had 2 12v batteries, little smaller than an auto batt.  Didn't write down the amperage tho...The batteries were visually inspected for bowed or expanded sides, cracks, oxidation.  Everything appeared in order.  They have likely been sitting for some time.  Stupidly, I did not check electrolyte levels.  Oops.  Could easily be low.  I plugged the charger into the mainboard for 30 minutes, watching closely.  No issues, no overheating.  I left it for another 2 hours.  Again, no noticeable issues.  I tested the drive motors by controlling it around my driveway briefly. Power was very low.  It worked, but clearly lacked juice. I plugged the batts in for another 4 or 5 hours.  But after that time, I noticed a crackling/squealing (faint) sound.  As if pressure was escaping.  Bad news.  I had the chair chassis (and batts) in my workshop, and now I was afraid it may blow, contaminating everything.  The batteries feel warm. One more than the other. Beginning to panic, I threw on my goretex, respirator, goggles and gloves and carefully detached the battery cable from the main board.   I've never had one of this size blow, and have no idea what it could do.  very hesitantly, I rolled it into my garage, and closed the door.  Now I'm afraid to sleep, because I'm concerned about it. Is this Normal old battery behavior?  Could this be due to low electrolytes?  A small crack in the case?  Is there anything I can do besides wait?  I'm not real anxious to go too close for too long.  Is there anything I can do that would not increase hazard?  I'm about to throw a tarp over it, but is there a high flammability risk if a high amperage 12v were to blow? Guidance highly appreciated.  Thank you.

Posted by huck alexander 6 years ago


Rescue a defunct phone charger

I have an old cell phone charger that is very handy for charging my Kindle Touch and a set of Bluetooth earbuds. It quit working one day after someone used it to charge a high demand device. I read that the capacitors in these often fail. I got two electrolytic capacitors at a surplus store for less than a dollar total. I had to use a fine saw to open the plastic case. The new capacitors were the same electrical size, but not the same physical size. Closing the plastic case was not an option. I covered all exposed electrical contacts with hot glue, which is an excellent insulator. It looks ugly, but I have a good versatile charger again. (The high voltage connections are buried deep down where my fingers can not reach. As best I can tell, the terminals covered with hot glue for insulation are all low voltage.)

Posted by Phil B 7 weeks ago


Distortion pedal project

I was planning on making a motion detector with my roommates but that proved a difficult first project so now we have the plans for a distortion pedal for guitar.Here is the design for it and here is where we are going to buy the equipment (except for the audio jacks which we bought at Radio Shack already).Here are a couple of things we need to know first:1) The plan calls for two 10uf electrolytic capacitors, and the store has those but of 5 varieties with different voltages, which ones should we get?2) What kind of capacitors do we need? Ceramic disk?3) The plans call for a 0.0056uF capacitor yet I couldn't find one like that, can I just substitute one similar? If so, which one?4) If anyone wouldn't mind, could someone explain how this circuit works? Preferably answer the other questions, but I would like to learn how it works also.Thanks a lot to all who answer!

Posted by gohuskies 9 years ago


Electrolytic vs supercap for CD spotwelder?

I need to make a cheap spotwelder to rebuild some battery packs(e.g,. welding thin nickel strips).My options are:(a) Try to find most of a farad at up to 25V or so on eBay. This could take a while. (Buying new electrolytics in the 0.1F range and above at these voltages is pretty expensive.)(b) Go for supercaps from Digikey (e.g). They've got some 5V 1F models for only a few bucks, and some "fast-discharge" ones for 10x more. Of course, if I go for more than 10V or so, I'll have to build some sort of charge-balancing circuit around the series caps, and I'd rather not unless it's really the best way to go--- though it might be as simple as a resistor in parallel to each cap.(c) Try one of these weirdo "digital supercapacitors" that are all over eBay for the crowd who fill their entire trunk with stereo amps. These look like they're rated at 1-5F at 13.8V and (I would hope) include some sort of charge balancer. Dunno if they're suitable for the sort of instant-discharge I want for a welder, though.I'm having difficulty figuring out:(a) How fast a discharge I need for a spotwelder anyway; I'm going to be using an SCR to trigger it and presumably want the lowest-inductance arrangement I can get, but are we talking milliseconds or microseconds?(b) What can I get out of a supercap? Milliseconds or microseconds? I haven't worked with supercaps before, and most people who seem to be designing circuits with them are using them as batteries.Other random questions:My reference design had 0.5 to 1F at 0-25V through a 600V 50A TO-65 SCR; whatworries me are things like http://www.avxcorp.com/docs/Catalogs/bestcap.pdf,whose page 3 shows that non-ultra-low-ESR supercaps (e.g., theaffordable ones) seem to have virtually no capacitance for pulsewidths of 10ms or less. (The BestCaps in that datasheet claimsomething like 60% of nominal instead, which is pretty good!)I dunno how narrow the pulse width needs to be to get good welds,but I'm guessing pretty narrow---for example, one guy claimed inhttp://www.philpem.me.uk/elec/welder/ that just the difference inputting the SCR on the low side and not the high side (so the triggerfor it didn't have to go through the wires, electrodes, and workpiece)worked a whole lot better, which implies to me that he might betalking microseconds. But I just don't know.]Of course, I also don't know whether I need 0.5 F at 10V or 1F at25V for the things I'm considering.Not to mention---the 50F caps at http://dkc3.digikey.com/PDF/T072/P1354.pdf(some of which claim ESR's of 0.025 ohm at 1kHz) have these skinny little0.5mm leads on them. How in hell would these leads not be vaporized if Icharged up the cap and then shorted it, as a spot-welder would be doing?(And sure, I could try to attach #4 copper wire to them---somehow---andsend that to the sharpened tips on my welding electrodes, but boy I feelsilly doing that---seems like whatever part of the cap's leads aren'tattached to the heavy wire will just evaporate when shorted, if they canreally dump that kind of current, even if it -is- just for milli-to-microseconds.)The Instructables site has some rambling about using supercaps for CDspotwelders, but it's just rambling---nobody who's actually built oneusing them, for example, or who seems to talk about discharge rates,etc.

Posted by HilaryGage 11 years ago


5w Square Bright-White LED : Glow or Blow…??

Q: Glow or Blow…? Dear Friends…„ I dont know more about electronic and its power supply/consumption of electronic component. Recently, I seen and bought two components… (1) 5w LED (Square/White)  - Requires 9v ~ 12v DC (2) 1 Circuit Board (Readymade) Open LED Driver This Board has : 1x 474K 450v Polypropylene Capacitor 1x 1m Resistor 4x 1N4007 Diode Bridge 1x 100Ohm Resistor 1x 6.8uF Electrolytic Capacitor Nicely assembled. Open LED Driver run on main AC power of 230v. I havent test, connect and glows this 5w LED using this open board. I have tested this LED with 12v 2A LED-Driver…„ which was bought with LED-Strip at Diwali Festival…„ but with this 2A Driver this 5w LED only blinks not continuous glowing. I am confused…„ about this Open LED Driver…„ this my LED "Glow or Blow…?" I saw and design a circuit from this open driver…„ and sharing this with you hon'ble/s friends. Please Advice…

Posted by free2atc 1 year ago


DIY LED Sign with MAX7219 Dot Matrix Module STM8S003F3 MCU for AVR PIC MSP430 Arduino ARM STM32

To satisfy electronic DIY hobbyists, ICStation has developed MAX7219 Dot Matrix Module. It uses the Max7219 chip which do a great job on saving of MCU I/O. It can not only control each point individually, but also can be extended without limitation to meet your requirements on LED Sign, Team Logo and so on. What's more, it's controlled by the STM8S003F3 MCU with 1K data storge space which is low cost, low power consumption, very powerful. Major Building Portions of Electronic DIY Kits: 1. The 16pcs of MAX7219 Dot Matrix Kits are ready 2. Decomposition the pin header 3. Welding the SMD and max7219 Chip 4. Welding the electrolytic capacitor 5. Welding the pin header 6. Assembling the PCB 7. Setup the Dot Matrix 8. Wire Connection 9. Power the Dot Matrix and testing with our Code Follow the steps: https://www.instructables.com/id/DIY-LED-Sign-with-MAX7219-Dot-Matrix-Module-STM8S0/

Posted by ICStation 4 years ago


Do ATX Power supplies convert AC to DC power?

Hello all, I am sure this is a silly question for the experienced, but seeing as I'm just starting to really get into this stuff, any help would be appreciated. I am writing to get a bit of consensus to assure myself the a ATX power supply will convert AC power in to DC power out.  I would like to save myself the hassle of taking apart a computer if this is not the case.  In the event I'm wrong, what does convert AC to DC power? Just to give you an idea of what I need this for, this power supply will be used to run the electrolytic etching process for use with copper in a copper sulfate bath.  I'll be using the etch process to etch through copper plates (saves a lot of money compared to ferric chloride) The last question I had is if anyone knows how to discharge any residual energy within the ATX system.  I have an instructable on converting the ATX into a power supply, but I feel like I read the residual power in the system can be quite nasty if it shocks you, so I'd like to avoid that.  In fact, any suggestions would be welcomed. Thanks! Andrew

Posted by ajpaulette 8 years ago


Simple AM transmitter

I wish to make an extremely small (size and part count) AM transmitter using only a few transistors and passive components. I wish to transmit an audible tone on a set frequency.I am thinking along the lines of a transistor flip-flop circuit oscillator, perhaps routed through another. It really needs to have less that five/six small components. DIP components are too big. Small electrolytic and other capacitors, transistors, and resistors are acceptable. Transmission distance needs to be at least 1/4 of a meter, but further is better. It needs to run on between 1.5 and 6 volts, low to middle'in milli-ampage im thinking watch batteries for a few hours at least. I have read the following article but as stated before it needs to be very small. https://www.instructables.com/id/Make-a-simple-AM-transmitter/Can anyone help me out with a schematic, thoughts or advice?Thanks in advance,-AndyP.s. I can work out transistor loop timings and I understand how the Amplitude Modulation system works. Current thoughts/plans (if you can call them that) are an audible tone switching a secondary transistor loop from high (no resistor in series) to low (resistor in series) power and back. The secondry loop will be switching at the target frequency.

Posted by andy 10 years ago


HHO generator improves fuel efficiency of petrol engine!

Reproduced verbatim from The Fortean Times issue 249, republishing from FT35JUNE 1979On the 15th a demonstration of a "revolutionary" energy device took place at an undisclosed location in the UK. Iowerth Thomas, 58 a Welsh inventor, hoped to interest both government energy officials and an Arab consortium. Mr Thomas had been experimenting since 1936 with ways to make petrol engines burn more efficiently. His "bolt-on" device promised between 25 and 40 per cent efficiency using "the electrolysis of tap water", plus a cleaner exhaust. The government scientists' response - that it was impossible - spurred Mr Thomas to demonstrate it for them. He reported to the motoring correspondent of the Daily Telegraph that his stationary engine ran for 112 seconds with his device and for 77 seconds on the same amount of petrol without it. The usual objection to electrolytic systems is that the energy needed to run them is greater than that produced. With some sarcasm, New Scientist sniffed that the device needed to be much smaller than the room-size contraption Jones used. What really stoked their scorn was Thomas's reply when asked how it worked: "It's beyond me," he said. That was the last we heard of him and his promising device.How has this technology improved in the last 30 years?L

Posted by lemonie 9 years ago


Producing Hydrogen to Function as a Lift Gas

The short version: I want to make hydrogen to fill model airship envelopes with, because screw helium. Help me make a cheap electrolysis device that can do this in under an hour (ideally), or come up with an even better system for production. My immediate problem is that I need a high-surface electrode that won't fail in a solution of sodium hydroxide.The long version:I've devoted a fair portion of my time to contemplating airships, primarily because they're awesome. Fell out of use with the rise of much faster aircraft, and the technology its fate sealed by the extraordinarily bad rep the Hindenburg gave it. It is still far from useless, however, in that lighter-than-air systems can lay claim to flight times measured in days, and sometimes months, thanks to the fact that they literally float in the air like a boat floats in water.Their day may have come and gone, but I still want to experiment with the technology and create some model airships of my own. Helium works okay as a lifting gas, but it remains expensive and isn't going to get any cheaper in the foreseeable future. It is for this reason that I am pursuing hydrogen, in the hope that I might be able to produce a cheap lifting gas for my projects. Unfortunately for my aspirations, hydrogen is surprisingly hard to get cheaply in decent quantities. Here's what I've figured out so far.For one, it is absurdly hard to find sites that don't veer into fringe science when talking about hydrogen. HHO production, Joe cells, power your car with water...it all keeps cropping up, and not only does none of this do what I want, the concepts are often poorly documented or riddled with problems. However, I have been able to glean some information from my research. First off, one of the easiest methods (and the one I'll be pursuing the most) of hydrogen production is through electrolysis. For those of you unfamiliar with the concept, you can basically take two electrodes, stick them in water, add some electrolyte (like regular table salt), and apply a decent voltage. You'll get hydrogen gas streaming out of the negative electrode and oxygen out of the positive electrode. Fancier systems use large tanks, platinum electrodes, and a strong acid or base as the electrolyte. To increase efficiency (yeah, it's not 100% efficient), there is ongoing experimentation with high-temperature electrolysis and ongoing research into an effective electrocatalyst.Now, when I did my research, I thought "Hey! This sounds easy! I'll just set the system up like explained, and away we go!" Unfortunately, those exclamation marks were unwarranted. My first attempt showed that production is mind-numbingly slow with small electrodes. Using salt had the wonderful side-effect of producing chlorine and sodium hydroxide, a.k.a. caustic soda. It's called that for a reason, and I'm lucky I didn't run it too long or I might have a chemical burn now. Now I know. Choosing a good electrode turns out to be a problem too, as most conductors oxidize quickly or dissolve in the solution (now I know why everybody uses platinum when possible). My aluminum foil electrodes in a sodium hydroxide solution? Yeah, that didn't work AT ALL. I had better luck with steel mesh, but I recently found that it seems to fail over time too. The only thing that isn't disappointing is the container and the collection apparatus: an inverted plastic bottle with some airtight hose running off it, connected to a gas valve. If the bottle is placed such that forming gas causes the internal water level to be lower than the external container water level, the gas will be pushed through the hose (no pumping necessary!). There was one good thing I discovered, however. Apparently there was a bit of soap or something left over in the container, and I ended up forming a bit of explosive foam as well. The hydrogen foam blows up like nothing else, and the oxygen foam makes a loud pop and sends (slightly) caustic foam all over the place. Totally useless but still somewhat cool, so long as you're not fool enough to do it in large quantities.So, as of right now, I've got a good container and collection system, but my electrodes suck and production rates are so low that it'd take me hours and hours to inflate a good-sized balloon anyway. I'll be using sodium hydroxide in the future as the electrolyte, skipping the chlorine production and observing the proper safety procedures. My top priority is finding a good electrode, my next is finding a good way to increase surface area, and my last is getting a higher voltage source than the 12V power supply I had lying around. Any ideas?

Posted by Cognoscan 9 years ago


Passive mixers, I don't undertand why the resistor/capacitor

Hi, when I was young, our teacher show us a passive mixer, each input had only one green capacitor in series for each input, it was not electrolytic but ceramic or polyester, it sounded so good for just being there 1 simple component per channel. Now taking a look at google, can see that the most passive mixers, uses resistors to isolate sources, with values since 10k to even 100K. Other schematics shows a resistor and capacitor in series (see image below) what does that capacitor? and why some schematics only has a simple resistor? is it easy to calculate its ohm value?. Is it better using this configuration supposing that the source is weak (coming from cellphone 3.5 mini jack or RCA) and this mixer targets the signals to a pre amp? So I need to from weak sources like iphone, dvd, any RCA output, etc... anybody know whats the best to use in this case? Thanks so much. Should I put a resistor as minimum as possible? I undertstand that a resistor there, in the input, will reduce the volume input, and I dont want to do that, so can I simple connect everything direct? or the resistor isolates the inputs, otherwise it will sound ugly? I am very confused, why the resistor? why I have seen resistors from some ohms to 2km and even a lot more, 50k, 100k. I want to mix two weak sources, as a signal coming from a walkman and cd player, or cell phone, etc, so whats the law for not reduce signal intensity and mix everything well? all channels will come in into a pre amp IC.

Posted by destrip 2 years ago


Capacitor bank for Coilgun help please!

I havetwo 680 uF capacitors, rated for 200 volts.. And I want to use a disposable camera charger to charge them both. The camera charger stops at 300 something volts, and when I wire them up in series, I get 400 volts, right?.. I want to charge them and discharge them into a coil of wire to launch a projectile at a fair velocity. , I can work with up to 10k wraps of wire, and i have only two capacitors and a major one.. First 2: 680 uF 200v 680 uF 200v Major one: 180 uF 400v Now I imagine I'd get more joules with the two smaller ones than the big one because of the microfarads, right? These specific type of capacitors are made from Elite, and are electrolytic I think, and I got the major one from a computer CRT monitor, and the two smaller ones from a computer power supply.... I also have a 3.3uF 50v capacitor. Now the question is: Can someone help me add these together to increase maximum joule output? I want to hook up the two 680 uF 200v capacitors in series to get a maximum voltage of 400. Then I want to add the major capacitor, which is 180 uF in parallel with the two other capacitors to increase microfarads, in this case, it'd be: 680 680   + ------- = 680 (because they are in series) ------- + 180  = 860 I want two capacitors in series, and the major in parallel, increasing voltage to 400 volts, and the major capacitor doing nothing but adding capacitance (IF possible) Sorry, this is alot to ask for you guys to answer, If none of the above can work, What would work better, the two 680 uF's in series, or one big 180 uF 400 volt capacitor? I apologize if I cannnot explain my question properly.... it's very hard to understand capitance and series/parallel blah blah mumbo jumbo. Thank you.

Posted by Justdoofus 7 years ago


Arduino ADC & Decoupling capacitors.

Hello, I have a sample Analogue to Digital Converter from Microchip.  (MCP3901). Now I want to use this ADC together with an Arduino (Uno) on a breadboard  in order to connect it to my laptop.  This works all very smoothly and all by all I am fairly happy with the result up till now. But, there is a small problem.  There is a small oscillation in the data when measuring over something with a large resistance (first 3 graphs).  The oscillation is absent (or greatly diminished) over things with small resistance. (last 2 graphs). I have only a basic knowledge about electronics and cannot get rid of (or even diminish) the oscillation. My guess is that I don't get the decoupling capacitors right. These are the symptoms: Voltage measured across the solar panel of a calculator during ~2s  (while lifting my hand). Look at the oscillation in the data . (the oscillation is about 50Hz ) And zoomed in: Secondly, in the case of a 100 kOhm potentiometer in series with a 2.2 MOhm          (There is no Omega in the special characters list?) I can see that the oscillation is scaled with the measured voltage. This means that the oscillation is probably internal.  (My guess is that the source is from the power lines which are probably not decoupled very good. And the oscillation manifests itself in the internal reference voltage) So, this goes from 0 to ≃0.2 V  (because it is a 100kOhm in series with 2.2 MOhm between 5V and ground.) increased in small steps (small turns on the potentiometer) Green = without decoupling Caps. Red = with decoupling caps (0.1µC ceramic in series with 47µf electrolytic, but it's pretty much the same with all caps.) (the oscillations here are more sinusoidal than the ones with the solar cell) And finally, there is no problem when measuring over something with a low internal resistance. Look at this graph of a (bad) potentiometer or about 100 Ohm.  And look at the near absence of noise and oscillations in the data. I can't immediately see why the ADC gives such clear data in this case. But this is definitely what I want. And a detail; Has anyone some Ideas on how to kill that oscillation? (I don't mean with fourier transforms and such)  If the decoupling capacitors are the problem, I have a limited choice in themc can you please say which ones I should search for? Thank you very much.  

Posted by Sparticles 5 years ago