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  • Sponge + Ferric Chloride Method -- Etch PCBs in One Minute!

    I tried this method using vinegar and hydrogen peroxide as the etchant. The problems that I encountered were mostly answered here, but for some reason I did not see them. The first problem I encountered was when I tried to get the transfer of toner onto the copper clad. The iron-on method at the heat suggested by those using it didn't transfer anywhere near completely. I tried again with magazine paper which worked much better. But I still had to thicken up some of the lines and make the areas around the holes larger. I did that using permanent marker. I found a really fine line marker by the same maker of the other permanent markers. Still when I went to etch, the marker wore off and the etching process went on and on. But I get ahead of myself - the first try actually did absolutely n...see more »I tried this method using vinegar and hydrogen peroxide as the etchant. The problems that I encountered were mostly answered here, but for some reason I did not see them. The first problem I encountered was when I tried to get the transfer of toner onto the copper clad. The iron-on method at the heat suggested by those using it didn't transfer anywhere near completely. I tried again with magazine paper which worked much better. But I still had to thicken up some of the lines and make the areas around the holes larger. I did that using permanent marker. I found a really fine line marker by the same maker of the other permanent markers. Still when I went to etch, the marker wore off and the etching process went on and on. But I get ahead of myself - the first try actually did absolutely nothing. I waited and gently rubbed, but nothing happened. So being a reasonably smart guy, I decided that the vinegar I had was probably too old, so I stopped and went for some new stuff. That worked much better, but the marker wore off as I said.Thinking that I might have rubbed too hard, I remarked all of the etched off traces and tried again. Judging from the amount of solution I was using, my copper clad is too thick OMG - they are 1 oz boards. Well, that's ok, I'll try again with the remarked board and use a pan rather than a sponge. I did and things seemed to go along quite well. I kept the board agitating to keep the bubbles from forming - I got kind of a foam over the top, so I cleaned that off and turned the board over. Every 15 minutes or so, when the activity seemed to stop, I removed the board, dumped the old material into a container and put fresh etching solution in the tray. However, again I get ahead of myself. I noticed during the second try that the marker was coming off again. It appeared that the toner was holding up ok, but the marker was not.So I decided to remark the board a third time and try once more with the same result - so I let it finish. I refreshed the solution a fourth time and it took the last of the copper off with a woosh! The toner covered areas were ok , but they were not continuous so I decided to hand wire this prototype and see if it works while I determined what went wrong.I was able to wire the board and nearly got it working, still having trouble with floating inputs. And I decided a couple of 'pull-down' resistors were needed and I found an error in the logic, so not all was lost. Also the holes for the power connectors were in the wrong places, so I'll have to redo them as well.For the next board, I plan to use the sponge method again with vinegar and hydrogen peroxide to see if I can succeed in making good traces. The board is quite large 4.5" x 6.0" and two sides which I am doing at the same time. I am debating whether to drill the 550 holes first again. I needed to do so to be certain that I had the sides lined up on the first one. Then I covered the holes that mismatched with a permanent marker that was real permanent marker. I put the thick end of the marker into the hole and left a good sized circle around the hole, thinking it would partially etch off. It did for a few of them, but not all - so I ended up separating the copper using an exacto knife.BTW to drill the holes I used a standard bench press, cranked the speed to its maximum (3000 rpm) and mounted a portable fluorescent light with a lens to help me locate the holes. The only problem I had was that many of the holes had no copper around them because of the poor transfer. (I know - I should have not tried without a good transfer. But I needed to get a usable board right away. I did get some good out of it because I found some errors, etc.) Anyway, I was able to make reasonably good guesses at where the holes should be and it worked fairly well. I used the 1/8" shank carbide tipped drills available from Amazon. I busted one of them because I got too tired and forgot to let the press up before moving the board - snap! I used a 0.9 mm for the most of the holes and 1.1 for the holes that needed to be larger (I have a 50 pin DIP for I/O). I bought a bunch of 0.9 mm drills (not carbide) to try as well. i think I will put a small drill chuck into the chuck on the press to see how that works.I used a piece of plastic cardboard with a shop paper towel on top to keep the drill bit from getting broken. The shop towel did wrap a couple of times so I think something like Styrofoam might work better. The plastic corrugated board works quite well on top of the press plate but it needs something softer on top of it to accept the drill without going sideways and breaking the bit. I was going to use a Dremel tool but decided against it.Well sorry about the long post.

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  • Stop using Ferric Chloride etchant!  (A better etching solution.)

    Sorry I am not a chemist, but I am an engineer. I have used 12% and someone else here (maybe you) had used it too. So, I can't argue with you that it is not dangerous and didn't. But 12% is not nearly as reactive as you suggest. You couldn't get me near 30% so... Now after actually trying it with the Citric acid, I made one batch going from 3% in a ratio of 40 to 60. The next batch I used 12% with the proper proportion to get to 40 to 60 and it worked exactly the same as the first batch. No, I didn't go in there and measure temperatures, etc. But the exothermic reaction was benign at worst. (I had to wait almost a minute to begin to see bubbles appearing on the surface of the board in the tray.) This goes along in agreement with another post in here.I wanted to use my gloved hands to ge...see more »Sorry I am not a chemist, but I am an engineer. I have used 12% and someone else here (maybe you) had used it too. So, I can't argue with you that it is not dangerous and didn't. But 12% is not nearly as reactive as you suggest. You couldn't get me near 30% so... Now after actually trying it with the Citric acid, I made one batch going from 3% in a ratio of 40 to 60. The next batch I used 12% with the proper proportion to get to 40 to 60 and it worked exactly the same as the first batch. No, I didn't go in there and measure temperatures, etc. But the exothermic reaction was benign at worst. (I had to wait almost a minute to begin to see bubbles appearing on the surface of the board in the tray.) This goes along in agreement with another post in here.I wanted to use my gloved hands to gently agitate the solution, but it was taking too long and I could not keep the permanent marker on the board, so I used a tray. It took almost an hour to do the 4.5" x 6" two-sided board in the tray. I had to add solution every 15 minutes or so. I poured off the used solution and poured on new (I was only putting 16 oz of solution on and it took three times that, but the last one wasn't used up. The reaction was bubbles, not heat (this is citric acid, not muriatic)The next one I try, I am going to put the board into a pan big enough to hold a quart or more of solution and rig it so that I can agitate it. (I really should be putting this on the other hand-held etching instructable, but I put it here in response to your comments.)Any thoughts on that?

    Interesting - as I have said repeatedly, I would NOT use 12% peroxide. I mixed mine down to 3%. Then I poured the two together with no reaction that was perceivable. (Acid into peroxide.) When I used 3% with 5% Citric acid in a 40/60 ratio, it worked like a charm. I had most of my problems with the transfer onto the board. The printed paper would not transfer to the copper well. So I tried to use permanent marker, but it etched right off.My first try was a bummer - the acid was too old - it did absolutely nothing. So I bought some new stuff at WalMart and away it went. It took a quart of mixture to do a 4.5 x 6" board. But like I said it ate off the permanent marker and the copper under it. Where the toner was still on the copper, it worked well.I tried plain paper, I tried magazin...see more »Interesting - as I have said repeatedly, I would NOT use 12% peroxide. I mixed mine down to 3%. Then I poured the two together with no reaction that was perceivable. (Acid into peroxide.) When I used 3% with 5% Citric acid in a 40/60 ratio, it worked like a charm. I had most of my problems with the transfer onto the board. The printed paper would not transfer to the copper well. So I tried to use permanent marker, but it etched right off.My first try was a bummer - the acid was too old - it did absolutely nothing. So I bought some new stuff at WalMart and away it went. It took a quart of mixture to do a 4.5 x 6" board. But like I said it ate off the permanent marker and the copper under it. Where the toner was still on the copper, it worked well.I tried plain paper, I tried magazine paper, and now I have purchased some transfer paper and will try again when it arrives. So thus far, I have a big goose-egg.

    I think you should read soulofscience's response to my use of 12% a few entries above here - you could be 'playing with peroxide' and get your butt burned. Stick with the 3% is my suggestion. I have converted all of my 12% into 3% so I can make some more PCBs. Although I didn't see anything that gave me concern, I don't need to risk my neck over something so cheap as hydrogen peroxide. I had 3 16-oz containers of 'food grade' hydrogen peroxide that was to be used for medicinal purposes (internally) I balked. So now I have made all of it into 3% which is the only stuff you should be using according to soulofscience.

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  • Stop using Ferric Chloride etchant!  (A better etching solution.)

    OK, the term 'play with' is not comparable to 'using' - not funny, you knew exactly what was meant - it is not uncommon usage. But, yes, you are 'playing around'. Even your comment following that about levels of 'danger/fun' suggest that you are. And I have 'used' muriatic acid in several different ways, including in a pool (I better say 'and others'). The fact that you can buy it at a hardware store does not negate the power of it. HCl is much more potent even at a lower percentage depending on what it comes in contact with. If you get HCl on your hands, you will know it - that was the point. Vinegar, not so much. And I think it can be easily surmised that I was talking about it in the same vein as you were. The concentration available in stores for both - those would be the comparison...see more »OK, the term 'play with' is not comparable to 'using' - not funny, you knew exactly what was meant - it is not uncommon usage. But, yes, you are 'playing around'. Even your comment following that about levels of 'danger/fun' suggest that you are. And I have 'used' muriatic acid in several different ways, including in a pool (I better say 'and others'). The fact that you can buy it at a hardware store does not negate the power of it. HCl is much more potent even at a lower percentage depending on what it comes in contact with. If you get HCl on your hands, you will know it - that was the point. Vinegar, not so much. And I think it can be easily surmised that I was talking about it in the same vein as you were. The concentration available in stores for both - those would be the comparison. The change of meaning of your comparison just muddied the water. And no, the acids ARE different. One is HCl, the other is citric acid. Citric acid is not nearly as reactive as HCl. You can't usually obtain citric acid at higher concentrations in a grocery store, although you could make it higher. Citric acid in vinegar is cheaper by a long way. I can find vinegar in 12 oz container, while the muriatic acid is nearly a full gallon - it is not hard to figure out what was being indicated. Perhaps if I put them out for sealed bids on several thousand gallons of each, we could make a better comparison, but for what reason? You can even make vinegar at home, if you want, from produce that you have around the house... HCl not so easily done. The purity was not in question. Even if you reduced the concentration of the HCl, it would still react faster and stronger in the etching process. Again just an informed opinion.My point about the 'bare hands' is that it won't burn you and as far as the copper salts, how many things made of copper have you handled in the last week. Are you sure that they didn't transfer 'copper salts' to you? If you are that concerned about copper salts, you shouldn't even be doing this. Do the copper salts stay forever? Weren't they all over the environment in some quantity before we started? If this is a concern, does your instructable say how to dispose of them. What, not important enough to specify exactly? So what do you think is going to happen with all of this copper sludge? Just a rhetorical question.As I stated up-front - IMHO, the instructable is excellent. It is very usable. But I am going to see how it goes with a different acid - citric because the suggestion is that some had overheating problems and I am familiar enough with acids that I don't want to take that chance if I don't have to. I am not 'concerned' about HCl - I just would rather not deal with it, and it is very reactive.I will revert to this method if the other one doesn't work, but I think I prefer to use a scrubbing method rather than let it sit in the pan till it's done. Just an opinion. I know - you said I could do what I want, but the rest of your retort sounded more like remonstrance on being so ridiculous - hmmm isn't that ridicule?. Sorry, that is the way I am thinking right now. I am planning to try the method today.

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  • Stop using Ferric Chloride etchant!  (A better etching solution.)

    So what? Can you not read? Are you still not aware that you are talking to me about something that I never suggested? You will not find any suggestion to use 12% or anything higher than 3% in the etching solution. All my comment says is how to change 12% into 3% so presumably the person who uses 12% would actually use 3% in the mix, otherwise why convert it. That does NOT mean to put 6% or 12% into the acid, does it? Try to comprehend before you make statements like that.All your talk about danger this and reaction that is probably true, but it is not what is being suggested by anyone - at least not by the one to whom you are aiming your comments.As to your 6% comment at the end - people use the 12% to drink. That means they ingest it. First they mix it with water, but they build up to...see more »So what? Can you not read? Are you still not aware that you are talking to me about something that I never suggested? You will not find any suggestion to use 12% or anything higher than 3% in the etching solution. All my comment says is how to change 12% into 3% so presumably the person who uses 12% would actually use 3% in the mix, otherwise why convert it. That does NOT mean to put 6% or 12% into the acid, does it? Try to comprehend before you make statements like that.All your talk about danger this and reaction that is probably true, but it is not what is being suggested by anyone - at least not by the one to whom you are aiming your comments.As to your 6% comment at the end - people use the 12% to drink. That means they ingest it. First they mix it with water, but they build up to being able to drink it at higher concentrations. I don't remember now exactly what the concentrations are, but it is pretty high. I'll see if I can find it if you keep this up. Your warning about 30% is probably wrong too. I doubt that you can make hydrogen peroxide stable at 30%, but that is just a guess. I will tell you this, I have put 12% directly in my bathroom sink and all it does is bubbles a little on scum on the edge of the fixtures. That is all.

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  • Stop using Ferric Chloride etchant!  (A better etching solution.)

    If you read what I said, I did not suggest using higher concentrations of hydrogen peroxide - I just told them how to make the 12% into 3%. This is perfectly legitimate and not any more unsafe than using hydrogen peroxide at all. In fact, the 12% I am talking about is food grade and is ingested by people directly after they build up to it.

    IMHO: Although I think this is an excellent instructable, I think it has too many dangers. I am going to try the vinegar with hydrogen peroxide method proposed by another instructable and use the 'in hand' gentle washing with a sponge as described in another instructable. There also is a lot of good information in Robot Room about a program called Copper Connection - I have tried it and it is very good. A PCB maker has also provided a program called PCB Artist. Both of these are free, but I like the Copper Connection much better. The only reason that I tried PCB Artist was that it offered auto-placement of the parts. Unfortunately, it did a very poor job. I was able to use some of the program's techniques, however, and layed out the board much better. I have also purchased a Dell C1760n...see more »IMHO: Although I think this is an excellent instructable, I think it has too many dangers. I am going to try the vinegar with hydrogen peroxide method proposed by another instructable and use the 'in hand' gentle washing with a sponge as described in another instructable. There also is a lot of good information in Robot Room about a program called Copper Connection - I have tried it and it is very good. A PCB maker has also provided a program called PCB Artist. Both of these are free, but I like the Copper Connection much better. The only reason that I tried PCB Artist was that it offered auto-placement of the parts. Unfortunately, it did a very poor job. I was able to use some of the program's techniques, however, and layed out the board much better. I have also purchased a Dell C1760nw color laser (LED) printer and the output at high resolution is outstanding (1200 dpi). It was only $100, not much more than an inkjet.If you are wondering about what I consider dangers - just read some of the reports of people who tried muriatic acid. When a reaction begins to heat things up, it can get away from you. I have enough 'bad luck', I do not need to look for an accident trying to find a place to happen. I am not sure why these over heated and over etched, but Muriatic acid is nothing to play with. Vinegar on the other hand reacts much more slowly - is extremely inexpensive and I would not be afraid to use my bare hands to handle the PCB except that I don't want to put contaminants on the PCB. And the resulting compounds can be tossed down the sink. Or if you wish, recovered.

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  • JamesW440 commented on jimustanguitar's instructable De-Rust Your Old Table Saw1 month ago
    De-Rust Your Old Table Saw

    This is an interesting instructable and very well done. Please allow me add to the 'controversy' over WD40 by making this COMMENT:When you read an instructable, you might be doing so because you want to know whether or not it works for something you might be planning to do - not only for 'old table saw'. The folks who add their 10 cents are being extremely helpful. If you want a series of comments lauding the writer, the instructables will get bland in a hurry. The commenters are saying that they have used another method and why or how it worked. Perhaps they could have been more clear, but why make it into a controversy.- jimustanguitar has been very good about this for the most part in all of his responses except that you can tell the comments bothered him some. That said, it is not n...see more »This is an interesting instructable and very well done. Please allow me add to the 'controversy' over WD40 by making this COMMENT:When you read an instructable, you might be doing so because you want to know whether or not it works for something you might be planning to do - not only for 'old table saw'. The folks who add their 10 cents are being extremely helpful. If you want a series of comments lauding the writer, the instructables will get bland in a hurry. The commenters are saying that they have used another method and why or how it worked. Perhaps they could have been more clear, but why make it into a controversy.- jimustanguitar has been very good about this for the most part in all of his responses except that you can tell the comments bothered him some. That said, it is not necessary to 'bash' the comments, just say what is the issue with them. If you don't like discussion, don't read or write instructables because you are going to see it. And to the fellow that said WD40 is 'not good for our use' - that was not helpful. Unless you are planning to give a reason for your opinion, don't state one. Thousands of people have used WD40 for almost everything and have been very successful. This is not a controversy - it is a difference in usage. You use your table saw for fine wood and furniture or some such might mean to use wax or something else, so your requirements are different from those who use it occasionally to cut up a 2X4. Where do you get the high standing to make that kind of comment? You don't, so don't, it only starts a 'controversy'.And to diyj2 - in my opinion there has not been any criticizers or detractors of this instructable and I have read all this 10 months later. The only detractors was the response to the poor soul who had the temerity to suggest that WD40 works well and described how. He responded to the criticism. jimustanguitar answered him well, though he complained about controversy later, but others didn't - and your comment, diyj2, in your second sentence was unnecessary, added fuel to the fire and added nothing. Your comment would have been better without everything after the first sentence down to the last two. It also provoked me to comment on this other baloney. Now I'll throw another one at you - I use my table saw to cut up metal - it works great! But I have had some problems with rust, not severe. This instructable was very helpful and I might try the wax.I don't want to use WD40 and I saw some other products that I might try. Do you see what I mean now? I have been just wiping it down with mineral spirits, but I need something else to keep it. I don't want oil on it - too messy. So this instructable was very helpful to me, especially with the helpful comments of your so-called 'detractor-criticizers'. I hope you didn't take those comments or this one as being criticism of you or your instructable..

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  • JamesW440 commented on awall99's instructable Arduino Data Glasses For My Multimeter 2 months ago
    Arduino Data Glasses For My Multimeter

    Yeah to the 'looking away' comment - every time I look away, the probe slips off and I miss the reading or short two pins together with unknown consequences LOL.

    Yes, very clever and well done. The proposal requires Bluetooth and a more expensive multimeter. Wouldn't it work as well if you converted the display into voice? If you could intercept the display output or read the display from the outside the multimeter's case, wouldn't that do the same thing and cheaper? Then you could use the Arduino to output the audio based on a series of instructions you give it according to the content of the display. You could even have audio input to the Arduino to instruct it what to do.Put the unit over the face of the meter, ask the Arduino for a reading, attach the probes and ask for another reading, etc. The Arduino could be clipped onto the face of the meter and both put in your shirt pocket or clipped on your person (strapped on your arm).Alternatively...see more »Yes, very clever and well done. The proposal requires Bluetooth and a more expensive multimeter. Wouldn't it work as well if you converted the display into voice? If you could intercept the display output or read the display from the outside the multimeter's case, wouldn't that do the same thing and cheaper? Then you could use the Arduino to output the audio based on a series of instructions you give it according to the content of the display. You could even have audio input to the Arduino to instruct it what to do.Put the unit over the face of the meter, ask the Arduino for a reading, attach the probes and ask for another reading, etc. The Arduino could be clipped onto the face of the meter and both put in your shirt pocket or clipped on your person (strapped on your arm).Alternatively, why not just make the Arduino into a multimeter with the features that you want.I can see what you are after and this is a very clever design and implementation for your type of use. I, for example, would not like to try to look at the screen that your design uses and the expense of the project would be too great for my kind of use. I buy cheap multimeters and use the sound for continuity checking. I find it very useful, so if I could use both hands for other readings, an audio output would be better for me, I think. So your idea is good, but its application is somewhat limited in that it requires Bluetooth from the meter and a device tethered to your glasses (although cool looking). That is why I suggest reading the display - works for any meter. Should be cheap too.Good work, thanks for sharing!

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  • JamesW440 commented on noahw's instructable LEDs for Beginners3 months ago
    LEDs for Beginners

    I suspect that your situation is long since passed, but I think a single 3 vdc 2032 would run all of these lights if hooked in parallel. In other words, the two lights should have been wired in parallel, not series. I am assuming that these are LED lights. Place all of the switches where they will be located in your model. Once the switches are in place, wire the battery plus (+) to each switch. I am assuming that your switches are only going to 'break' the plus (+) line.Start with a wire that runs to the nearest room from where you want to place the battery. Run the wire from the battery plus (+) to the switch and then from there to the next nearest room's switch and so on until all seven switches are connected on their input side. (It might be easier to connect all of the first floor ...see more »I suspect that your situation is long since passed, but I think a single 3 vdc 2032 would run all of these lights if hooked in parallel. In other words, the two lights should have been wired in parallel, not series. I am assuming that these are LED lights. Place all of the switches where they will be located in your model. Once the switches are in place, wire the battery plus (+) to each switch. I am assuming that your switches are only going to 'break' the plus (+) line.Start with a wire that runs to the nearest room from where you want to place the battery. Run the wire from the battery plus (+) to the switch and then from there to the next nearest room's switch and so on until all seven switches are connected on their input side. (It might be easier to connect all of the first floor on one line and then all of the second floor on another line, but that part doesn't matter.) When all of the switches are connected on the plus side, connect the lights in each room to the plus (+) side of each light and then to the other side of the switch it will be operated by. None of these light connections should go to any other switch - just the switch in that room and NOT to the battery minus (-). Now all of the minus (-) side connections of the parallel lights should be run to all of the other minus (-) connections so that all of the minus (-) side connections are together and attached to the battery (-). One CR2032 should run all of it and the switches should control each independently.Now I suspect that there is a reason for wanting to wire the house and then show a resulting fault that an earth quake or something like that would have on the wiring as the house falls. You might want to wire each switch directly from the battery plus (+) to avoid a portion of the house falling from taking the power away from the rest of the house. You could run the plus(+) and the minus(-) together to each switch, etc. Perhaps the young man knows what the teacher is trying to achieve so that you can route your wires accordingly.

    I think the main reason that they recommend them is that they understand them. It takes more than hooking wires together to make it work. Would you guys please explain how you get this microcontroller to do anything at all? I think that you have to write a program, don't you? And don't you have to understand how to write that program into the controller as well? Can you modify the program when you find it doesn't work? Don't get me wrong because I think you are right. But we tend to go with what we know. This might all be fun for you, but not so much for someone who doesn't have the knowledge or inclination to attempt it.And another thing, I worked on a tractor that had an instrument panel operating off ordinary electric gauges. It had broken and for $200 the people who owned the tracto...see more »I think the main reason that they recommend them is that they understand them. It takes more than hooking wires together to make it work. Would you guys please explain how you get this microcontroller to do anything at all? I think that you have to write a program, don't you? And don't you have to understand how to write that program into the controller as well? Can you modify the program when you find it doesn't work? Don't get me wrong because I think you are right. But we tend to go with what we know. This might all be fun for you, but not so much for someone who doesn't have the knowledge or inclination to attempt it.And another thing, I worked on a tractor that had an instrument panel operating off ordinary electric gauges. It had broken and for $200 the people who owned the tractor replaced it with one that uses a microcontroller. It worked for awhile and then broke again. I looked at both the old one and the newer one and found that the old one was still operable, but I could get nowhere with the newer one because I couldn't find any specs on the microcontroller. I fixed the problem with the original analog panel and it works fine. (BTW, the problem was that the ammeter in both units overheated and burned things up. (There is no connection between the ammeter and the other gauges except proximity.) I could find no reason for the overheating so I took the ammeter out, tied its input and output wires together outside of the instrument panel and replaced it with a cute little digital voltmeter. No problem since.)

    The situation here is what resistor do you use when the LED and the voltage source are the same? What should be done to overcome the 'no resistor needed' situation? You can approach it by increasing the supply to a higher value or look at the spec sheet to find out just where 1.7 v is and where 20 ma is with regard to the device specs. If the 20 ma is the optimum operational current for the diode, then design to that current. If the light output doesn't change appreciably, try using a lower voltage. That is, suppose the diode works ok at 1.5 vdc at 20 ma. 1.7 - 1.5 = 0.2 v. At 20 ma the resistor in series with the diode would have to be 0.2/0.02 = 10 ohms. That would work, but the resistor really should be larger, so it would be better to up the source voltage if you can. The 10 ohm re...see more »The situation here is what resistor do you use when the LED and the voltage source are the same? What should be done to overcome the 'no resistor needed' situation? You can approach it by increasing the supply to a higher value or look at the spec sheet to find out just where 1.7 v is and where 20 ma is with regard to the device specs. If the 20 ma is the optimum operational current for the diode, then design to that current. If the light output doesn't change appreciably, try using a lower voltage. That is, suppose the diode works ok at 1.5 vdc at 20 ma. 1.7 - 1.5 = 0.2 v. At 20 ma the resistor in series with the diode would have to be 0.2/0.02 = 10 ohms. That would work, but the resistor really should be larger, so it would be better to up the source voltage if you can. The 10 ohm resistor is better than none.

    Nothing wrong with a voltage divider circuit. There is also a thing called a voltage regulator that will do an astounding job at maintaining the voltage at whatever it is designed to produce. Some have built-in adjustability. Others are set voltage like LM7805 which is a 5 vdc version (and inexpensive), so you would need to find a 6 vdc version. In fact there might even be one built into the device, but I doubt it. If so, it might handle 9 vdc.And, no, they won't take what they need and disregard the rest. It depends on what is in the package that runs the device at 6 vdc. If it has a regulator or a voltage divider that somehow handles the 9 vdc, you will have lucked out. Otherwise, you have toasted it most likely.

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  • Stop using Ferric Chloride etchant!  (A better etching solution.)

    This is a neat method. I would suggest looking into the 'sponge bath' method that another person used for Ferric Chloride etching. That method should work with these chemicals and allow one to make only enough to etch the current project plus not overheat everything because you have control over how much etching is going on at any given time. I would not want to risk putting that much time and money into making a pc board and then have it etch so fast that it overheats everything. You might be a little apprehensive about putting your hands actually into this stuff, but use a slower reacting mix and it should do fine.

    There is a pure 12% hydrogen peroxide available, but it is expensive by comparison. You can google it. I would not recommend using that peroxide you found with that other stuff in it! To make the adjustment from 12%, you do ratios 0.12 per unit vs 0.03 or 12/3 = 4 so you need 1/4 as much 12% to get the equivalent of 3%. Then adjust the volume for the amount you want to mix. As far as the acid/peroxide turning brown, it sounds like you got some sort of reaction - were you using Muriatic acid, or something else (a combination cleaner of some kind)?

    If you have 10% and you need the amount that would be required to equal 30%, you just do ratios. So you need 3 units of 10% to equal 1 unit of 30%.Adjust the total amount of liquid volume to get the right volume. So 2 units of peroxide with 1 unit of 30% gets 3 units of volume. To adjust that to use the 10%, you need 3 units total so 3 units of 10% plus 2 units of peroxide is 5 units 3/5 + 2/5 = 1 so 3 units would be 9/5 + 6/5 or 15/5 = 3 units. Put another way, you need 1.8 units of 10% acid and 1.2 units of peroxide to make the 3 units, not 1:1. So your etchant should have worked considerably slower at 1:1.

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