• Electronics and Embedded Programming V2
    1,309 replies, posted
[QUOTE=Goz3rr;34290340]What kind of ohm resistors would be most useful? (ie for using leds) and what µF caps? And do you have some kind of store that sells them in bulk at decent prices and ships to NL? Since i only own some from taking stuff apart, and local hardware stores charge 2 euro per LED etc.[/QUOTE] I highly recommend [url]www.bitsbox.co.uk[/url], they do cheap and fast international shipping and you can get resistor kits that contain a selection of common resistor values, the 1440 resistor kit is great value for money since you don't want to end up having to put resistors in series / parallel to get a certain value. They also sell an electrolytic capacitor kit that ranges in value from 1uF to 1000uF which is good for most things, however you should get a few lower value ceramic caps as well such as 100nF, 10nF and 1nF which are useful for certain things, if you have the money to spare they do ceramic capacitor kits. Besides that I'd recommend at a minimum some 1N4007 rectifier diodes, 1N4148 signal diodes, 2N3904 NPN bipolar junction transistors (or similar), a few op-amps, DIP switches, cheap multi-turn potentiometers and grab a pack of LEDs from ebay (the cheapest place). I assume you have a multimeter, if not I suggest dealextreme for buying one, do not spend less than $30 to avoid buying utter garbage, make sure it's fused (on all current sockets), has autorange, can measure AC and DC current down to microamps, continuity function, diode check function and has decent quality probes.
I've expirienced 220 ohms to be pretty universal for LEDs
Conrad managed to send me 10 huge crocodile clips instead of 10 100µF capacitors, great.
After some talking with VistaPOWA, i'm probably getting this: [img]http://puu.sh/dTWL[/img] And a ARDUINO MEGA 2560 R3
your missing electrolytic caps
O hi guis. I just finished a project for school, Quadrocopter with an uno and a special shield ontop of it with the gyro etc. Not much really. Is this even worth posting? Oh, DrLuke, I never told you but mad props on that scope of yours. I really do like it. Vintage soviet equipment :D And this: [QUOTE=ddrl46;34095022]Been desoldering parts from the boards I got out of the Panasonic TV, lots of goodies! [img_thumb]http://i.imgur.com/pCTcZ.jpg[/img_thumb] All of the ICs you see there had to be soldered from the board, none were in sockets.[/QUOTE] That video modulator. collect them. They make great tv transmitters (makeshift ofc)
[img]http://i.imgur.com/ohPRh.jpg[/img] I love 555 timers!
I very quickly this evening managed to hook my NES controller up to my arduino and interface it with my computer. This means I can play the original controller with emulators ^^ the only issue I'm having is the keyRelease function on the processing Robot class is fucked.
Playing around with Processing + Arduino in a class, making cool generative art with sensors and shit. I have a bigger final project, gimme some ideas, we have Arduino Unos, flex sensors, light sensor, pressure, IR, sliders, LEDs, and I'm gonna get some cool stuff from sparkfun
Alright everyone, here it is. It still needs some more optimization, probably with the Pi filter. Or should I simply a few things? [IMG]https://sites.google.com/site/lonewolfscircuits/sitefiles/Tele-TalkV2-1.jpg[/IMG] Opinions? EDIT: The Audio input going into the pre-amp is from the AF output.
[QUOTE=LoneWolf_Recon;34327339]circuit[/QUOTE] The power supply battery / DC diodes is a bit dodgy, since if the input DC voltage is equal or less than the battery voltage current will continue to be drawn from the battery (maybe you want this or maybe not) having a higher voltage DC input I.E 12V would solve this. As for the audio pre-amp part you don't need that extra capacitor C2 on the schematic since the signals are AC coupled from the previous stage (audio inputs), I would also increase C4, C5 and C6 to 4.7uF to avoid attenuation of low frequencies, if you just using this for voice then 1uF is fine. The gain of the pre-amp is a little on the low side, assuming your mic input is from a electret mic you can expect 50-200mV at normal talking volume, given the gain of 3.33 this will give you an output between 166.5mV and 666mV, I would suggest increasing the gain to 10 or more. Your emitter follower is not an emitter follower, I suggest you recheck your design there. As for the filter, final amp and antenna matcher I'm no expert at RF but the biasing of Q4 seems a bit poor (voltage divider bias is usually to be preferred, unless this has some advantage at RF), I also can't quite see the purpose of the filter, what are you trying to filter out ?
And shouldn't filters usually go [i]before[/i] the power amplifier?
[QUOTE=ROBO_DONUT;34328799]And shouldn't filters usually go [i]before[/i] the power amplifier?[/QUOTE] In this case the input should be fairly clean RF so there is no need for a filter, as for an output filter I don't see the need.
[img]http://i.imgur.com/YlhNt.png[/img] I've made a simple breakout for the atmega32u2 so I can play around with it. I will etch it within the next few days and solder the parts on when they arrive. I'm using right angle SMD headers on the edges instead of through-hole headers as I don't have a drillstand and it's [del]impossible[/del] highly unlikely to drill holes that size by hand.
The filter on the final RF stage is a Chebyshev Pi Low Pass. I stuck it in there to prevent any harmonics and limit the tuning range to the FM band. The pre-amp was giving some acceptable gain earlier, running about 4.6 minimum (The input signal was at 80Hz), I've dropped R8 down to 2K to bump the gain up to ~6.5. Any more gain and I think I'll have some distortion. Also, the mic I'm using is fairly sensitive and will be near my mouth(It's part of a headset). It was well heard through a my single transistor FM transmitter, but I'll check into it some more.. I've also bumped the wall wart's voltage to 12V like you said (Thanks for that btw) The emitter follower is still the one thing that is puzzling me. I've been using these as sources: [URL="http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/npncc.html#c2"]http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/npncc.html#c2[/URL] [URL="http://forum.allaboutcircuits.com/showthread.php?t=6977"]http://forum.allaboutcircuits.com/showthread.php?t=6977[/URL] As well as wikipedia, I figured that R11 would be the approx output impedance and just found the other values from there. I modeled my RF Amp off of these: [URL="http://talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-2.html"]http://talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-2.html[/URL] So I'll go back and recheck the biasing. Thank you
Your taking the output of the emitter follower from the collector rather than the emitter.
[QUOTE=Chryseus;34331093]Your taking the output of the emitter follower from the collector rather than the emitter.[/QUOTE] *facepalm* Thanks, that's the mistake I make after working at it for a few hours :v:
[QUOTE=LoneWolf_Recon;34331155]*facepalm* Thanks, that's the mistake I make after working at it for a few hours :v:[/QUOTE] It happens <3
[QUOTE=LoneWolf_Recon;34329649]The pre-amp was giving some acceptable gain earlier, running about 4.6 minimum[/QUOTE] My bad I forgot to take the parallel resistance into account, as drawn it has a maximum gain of 5.33, with a 2k resistor this will increase to 7 and give an input impedance (looking into the base) of 143k, assuming &#946;f = 100. As for emitter followers the emitter resistor determines two things, the input impedance and the output impedance. The input impedance being &#946;f * R and the output impedance being R. Generally you want Zin to be 10x greater than the source impedance (including the base bias)
Lets make some music! [url=http://i.imgur.com/CE8mj.jpg][img]http://i.imgur.com/CE8mjl.jpg[/img][/url]
[QUOTE=ddrl46;34343715]Lets make some music! [url=http://i.imgur.com/CE8mj.jpg][img]http://i.imgur.com/CE8mjl.jpg[/img][/url][/QUOTE] What camera/lens do you use? Probably been asked before but these shots are great.
[QUOTE=ruarai;34346857]What camera/lens do you use? Probably been asked before but these shots are great.[/QUOTE] Canon EOS 20D with 28-105mm f/3.5 - 4.5.
Almost everything you need to build a capacitive discharge spot welder! [img]http://eagle.undo.it:8083/img/cdwelder_07_small.jpg[/img] ...just waiting on the chassis. I'm tired of lugging around a charger for my netbook; hopefully I get that last piece soon. Just in case you want to source one, that foot switch was designed for a tattoo machine. Get it on eBay - Hong Kong's miscellaneous electronics outlet.
Oh god, you didn't honestly buy a car-audio-cap, did you? They're overpriced as hell!
Can't tell if serious or joking. It's either spend $40 on that or spend $400 on equivalent tech-grade caps. Cap was independently verified by a somewhat trustworthy source to be 0.932 F with an equivalent series resistance of 1.52 mohm @ 20Hz. Worth the gamble considering the cheap price. Do note that [i]most[/i] car audio caps are overpriced as hell and do not actually come anywhere near their advertised capacitance. Be very careful when choosing one - the one I purchased is a Scosche ECAP1.
[QUOTE=DrLuke;34374954]Oh god, you didn't honestly buy a car-audio-cap, did you? They're overpriced as hell![/QUOTE] I'd really love to know where you get your information from..
[QUOTE=Night-Eagle;34375334]Can't tell if serious or joking. It's either spend $40 on that or spend $400 on equivalent tech-grade caps.[/QUOTE] [url]http://www.youtube.com/watch?v=EoWMF3VkI6U[/url] 2600F for about 15USD. Yes, 2600 farads. Yes, probably MUCH higher ESR and lower voltage. But still, 400 dollar is nonsense.
[QUOTE=masterburner;34375384][url]http://www.youtube.com/watch?v=EoWMF3VkI6U[/url] 2600F for about 15USD. Yes, 2600 farads.[/QUOTE] 2.5 V. That might be uF, as well. Common mistake. I'll research it, though. Okay, yeah, he says it's Farads. But can you actually source those for $15?
[QUOTE=Night-Eagle;34375439]2.5 V. That might be uF, as well. Common mistake. I'll research it, though. Okay, yeah, he says it's Farads. But can you actually source those for $15?[/QUOTE] [img]http://i.imgur.com/dn7S7.png[/img] Just checked at that store though and can't seem to find them, but did find [url]http://www.ebay.nl/itm/Maxwell-2600-Farad-Capacitor-2600F-Boostcap-Ultracapacitor-2-5V-BCAP0010-/270825328358?pt=LH_DefaultDomain_0&hash=item3f0e728ee6#ht_1464wt_1163[/url].
Yeah, I checked the website before I posted that. I can only find them on eBay for $40. Correct me if I'm wrong, but I see a problem in my application with the cap you refer to. For CDSWs, we require high current for a small amount of time. Discharging this 2600 F capacitor with a thyristor without a blocking circuit will result in a longer (by an order of magnitude) burst due to the higher capacitance, whereas a CDSW requires only a short burst (on the order of milliseconds to avoid overheating the work). To fix this, we would have to add a blocking circuit to the thyristor or replace the thyristor with something else. This sounds complicated and expensive. Obviously I'm not going to scrap everything I have if it works like it has for others in the past, but it is an interesting idea.
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