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every time I try to understand how an opamp works I have an internal dialogue not unlike one of those cartoons.
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Jan 8, 2008 05:13
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Squier posted:I am working on my senior year physics project which is a small cyclotron and need some electronics help. I need to create an RF amplifier that is capable of producing around 50-100 watts in the 1-15 MHz range. I haven't had much practical electronics and am hitting brick wall after brick wall trying to design this. So far it seems a push pull tube amplifier would be my best bet but am really lost beyond that. Any help at all would be awesome. Tube amps are very high impedance and voltage devices. Tube circuits are simple and you can get crazy power out of them, but you need to work with very high DC plate voltages that may give you a heart attack if you take it across the chest. Generally you need forced air cooling over 300w or so, but you should be fine. Cooling tubes is way harder than silicon as you can bolt transistors to a heatsink, not so much for a set of 6L6's. Transistor amps deal with lower voltages but high current, and the matching networks are pretty different. In the 100w range you should be able to easily find a single IC that will amplify what you need; if you have to build it discrete, I understand, but the chips are out there to solve it. Have you been given specifications as to how much filtering/etc you need on the output? My only experience is with HF ham amplifiers and we have very stringent requirements on harmonic and spurious outputs.
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Jan 21, 2008 02:32
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pim01 posted:Can I ask a stupid question? I'd like to add an extra output to my dac, but I'm unsure if just placing the new one parallel to the existing one is a good idea. Wouldn't that efficitively halve the amplitude of the signal on both outputs? Nope, remember, paralleled circuits have the same voltage but half the current. This means that if you take your output and connect it to parallel outputs A and B, each one has an impedance twice that of the original output - meaning less current available. However, most stuff these days has pretty high input impedance and you should not appreciably load the circuit. I would recommend placing 1k resistors or something similar in line with each paralleled output to give better isolation. If you want an active solution, just get a single-rail dual opamp and build a pair of voltage followers - + input is signal, - input is connected to the opamp output. If it's stereo, just make a pair of circuits, one for L, one for R.
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Jan 21, 2008 21:00
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I'm about to make Futurlec richer and need some advice. I'm just wanting to stock the junkbox. I've previously purchased about $40 of assortments and kits from VAKits; the prices are OK but I need more components and their selection is meh. I want to get a breadboard development setup and start messing around with analog circuits at first, moving up to TTL and CMOS in a bit. I also want to perhaps play around with RF stuff at the HF/VHF/UHF level (preamps, converters, simple stuff like that), built dead-bug style on the stack of copper clad boards I have here at my desk. Anybody want to help me come up with a basic shopping list to stock the cupboards? I have good starting stock on resistors, ceramic and electrolytic caps, 1n914's and 1 amp power diodes. 1x basic DMM - $5 -1x 390 point breadboard - $6 -1x 840 point breadboard - $3 -1x jumper kit - $5 - 300 piece 1/4 watt resistor assortment - $2.50 - 100 Linear IC assortment - $6 - I have maybe 2 dozen op amp/regulators right now, want more - 100 Transistor assortment - $5 Now I'm wanting some suggestions for some components I should grab by the dozen. Thinking 2n3904/3906, LM2902's and LM2904's for opamps, voltage regulators in 5v/9v/12v, a couple cheap TO-3 or TO-220 power transistors, maybe some FETs (mpf102 for radio circuits?)... Any thoughts for good 'starter parts'? I like cheap, flexible parts; money's tight these days. Edit: My first project will be to grab a power transformer from Radio Shack and build a 5v/12v/variable voltage power supply - 1 amp on each should be plenty room. Jonny 290 fucked around with this message at 23:18 on Jan 24, 2008 |
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Jan 24, 2008 22:43
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The Radiskull posted:Here are some bits ive got to Build an amp. That transformer (the 530 VA one, the only one you should consider for this project) will suitably drive an amp up to about 250, maybe 275 watts maximum without exceeeding its ratings. From what I remember, linear power supplies are about 50-70% efficient depending on the design. Here is a design for an amp based on those transistors. This would be a good design for you to start out with.
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Jan 25, 2008 22:25
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Yeah, they have RF field strength meters and they're trained to know when X transmitter is close enough to see. Direction finding gear is pretty snazzy - I used to foxhunt back when I was a kid. Learning news: OH GOD I FIGURED OUT HOW JFETS WORK. I built a little lovely preamp in Multisim and it's dutifully amplifying my little 10 mV signal to 50mV with much better output impedance. Am I to understand that I shouldn't be looking at JFETS for low impedance (<10K ohm) circuits? They seem very sensitive to high-impedance signals but not really able to give low impedance outputs, no matter how I set the biasing resistors. I also got a nice unity gain JFET amp for 10 MHz going, as I need it to use as a buffer between an IF stage on one of my scanners to my ham rig's RX antenna input, without loading the scanner stage. Using an MPF102, going to mock it up this weekend.
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Jan 26, 2008 05:18
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It depends on the CB set, more specifically, how overbuilt it was at the factory. Some use output transistors that poo poo the bed at 12 watts; others will easily 'swing' 30. I'd say that most truckers are running between 25 and 100 watts with their peaked-and-tuned radios. Sky's the limit if they're hooking up amps. Now this means in no way shape or form that you are putting out more _clean_ power. If the radio is designed in a lovely manner, as soon as you set it for more gain, harmonics show up. Any time you are operating near the performance envelope of an active device like a transistor or tube, you're going to get distortion and harmonics. This is why people hate CB'ers who run too much juice - it's not how loud you are on 19 that bugs the FCC, it's the poo poo you spew out from channels 1-40 and higher that annoys people.
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Jan 26, 2008 05:53
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sithael posted:I know people say it about the waiting times on futurelec, but honestly, i've had an order in since November 28th and i'm still waiting on a common item (piezo buzzers?). I emailed them and got an answer the first two times, but they haven't bothered responding to any more. I needed the parts for school but i ended up just ordering from Jameco and they got here in two days, everything was alright except no ceramic caps, an extra bag of switches (mostly dip switches), the "pot assortment" is all trimmer pots, and resistor assortments that were either 470k or 6.8ohm. I'll admit I don't feel good about my Futurlec order until it comes in. They say they processsed it today, so that's a 3 or 4 day time so far. I like their store a lot because they have selection, but it's not a Mouser-type gigantic selection where I'm staring at 78 varieties of an LM386 trying to figure out which one I want. I'm not quite to that point, and I like assortments and 'packs' much more than buying 10 of each component I think I might need - after all, my experimentation is open ended and I don't know exactly what I want to build when I order the parts, just have general ideas.
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Jan 28, 2008 23:10
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mtwieg posted:<current sources> You just got me to understand current sources. Awesome. To test, I mocked up a cheap 2n3904 amplifier and for bias, I built a 2n3906 positive current source using a pair of 1N914's and a resistor to drop 1.2v at 1 mA. Pulled the base bias off that Vcc-1.2V junction and used a resistor to bias the transistor for 1 mA current. Perfect!
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Jan 31, 2008 10:13
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kid sinister posted:According to the stats on those bad caps, I'd need some 2200uF 6.3V caps and some 1500uF 16V caps. Do I just need to match up those numbers for replacements? You need to match the uF values and meet or exceed the voltage values. Note that capacitors come in varying tolerances and temperature coefficients - if you grossly mismatch these secondary characteristics, things may go south. however, you should be A-OK if you stick with high quality capacitors.
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Feb 6, 2008 05:49
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Here's the trick. Open collector transistors can 'sink' (or provide a ground for) a higher voltage than your TTL supply voltage, up to near the voltage limits of the transistor. They are also conveniently active-high (they provide a ground at the collector when there is + voltage, and thus bias current, at the base, relative to the emitter.) Thats how you could switch a 12v source with your TTL level signal. Edit: Yay, my Futurlec order came in. 11 calendar days from order to delivery, and I got a bitchin' PACKAGE OPENED AND INSPECTED BY US CUSTOMS sticker off of it. The $2.95 multimeter is just fine for beginner work, and the breadboards are heavy and solid - I am very impressed with them. Jonny 290 fucked around with this message at 02:00 on Feb 8, 2008 |
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Feb 8, 2008 01:58
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OK, help me wrap my head around this one. I created a touch sensor out of a common collector amplifier with a 2n5306 darlington, a +5v bias voltage (for 4.3 at the emitter) and +12 fed to the collector (it's what was set up on my board at the moment). Load is a 2.2v drop LED with a 47 ohm resistor (ignore the bad sizing for now). Like a good Darlington amp should, I get full current through the LED when I touch the Vbias with one hand and the base with the other. HOWEVER, when I touch my hand to only the base, the LED dimly lights and I measure about 43 mV across the load resistor, calculating to about 600 uA of current flowing! Dividing this by average Darlington gain of 10k, I get a base current of 60 nA. Is this body capacitance at work, or what the hell is going on?
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Feb 9, 2008 05:42
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I just wowed and amazed my co-workers by hardwiring a laptop power supply to the broken jack on a 3-month old Compaq that somebody brought into the PC repair side. "2 hours billable" beats "Sorry, we can't fix that." They're tickled pink. Learn to solder, learn electronics, and know the right time to show your hand and you'll make a tech's day.
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Apr 11, 2008 20:29
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babyeatingpsychopath posted:
Instead of using the resistor network to cut down the regulated DC, learn how to use resistors to make a regulator work at any voltage. Presto, variable DC supply. Now, the regulator will give off X watts of heat, where X = (voltage difference between in and out pin) * (current passing through), so you don't want to regulate 15 volts down to 3 and then draw 2 amps of current.....
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Apr 14, 2008 19:02
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Troubleshootin' time! I'm attempting to build a direct-in box for my bass and 6-string guitar to use as an input preamp/isolator to the line in of my Macbook. Concept: Unity gain follower on the input, driving a voltage divider level control, driving a 101:1 voltage amp, into a current amp biased for about 60 mA collector current. The LM324 was in my junkbox in quantity and seems to be able to source plenty of bias current. Here is the circuit that I have cranked out. It looks okay when simulating, giving up to a 101:1 voltage gain and driving a 100 ohm load like gangbusters. I built it up last night adhering to the schematic and in the real world, I get terrible,terrible distortion at all levels. I'm suspecting that I've got something retarded going on with the various input/load resistors. I am not too good with level controls, or op amp load/input resistors. I tried to get by but it certainly sounds like I boned something up. Here is the schematic. Does anybody see glaring problems that might cause this? Am I running too much collector current? Output resistor is 4x 470 ohm in parallel for a 115 ohm 1w resistor. 
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Jun 11, 2008 20:00
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Yeah, I'm teaching myself AB amps on the side and they are screwing my head pretty good. That's the next stage, after I can figure out how to properly pick an opamp and get this one humming. I have a TL061ACN and a TL082CP in the parts box. I figure either of those would be a better match. Thinking about the power supply issue, I may just bite the bullet and build a dual rail linear supply off this transformer, rather than trying to BS with split rails and wall warts. Figure I could do that for under $20, and I need practice with linear supplies anyways. Further edit: Let's nail this bastard down so it works solid and I can contribute the interface schematic to home recording nerds down in ML! I see "how do i plug my guitar into my sound blaster" questions almost daily still. Jonny 290 fucked around with this message at 23:00 on Jun 11, 2008 |
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Jun 11, 2008 21:32
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Thermal noise is just that - noise generated by heat. Resistors and active devices dissipate a lot of heat. RF and interference pickup from coils is a non-issue generally unless you are working at high frequencies or in unshielded devices. Inductors have a 'low-pass' behavior. As the frequency goes up, their 'resistance' to the current goes up. Think of them as a resistor that is 0 ohms at DC, but high ohms at AC frequencies. Capacitor is the exact reverse - high resistance (open circuit, in fact) at DC, but low resistance at AC. This is how basic passive filtering works - an LC or RC filter is just a divider network similar to a resistive divider, but using an inductance and capacitance. Here's a high pass filter. code:code:As the frequency goes up, the capacitor will appear as a lower and lower resistance and the inductor a higher and higher one, effectively changing the tap point of the resistance network. Thus, more of this signal passes through to the output. For a low-pass filter, you just exchange the L and C components. The L will be on top, getting larger as the frequency goes up, and the C will be on bottom, becoming less resistive, effectively bringing the level down as the frequency goes up. And there, I just went on a tangent on filters on a work day. I know I mis-termed stuff and know about reactance but figured I'd simplify.
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Jun 13, 2008 18:43
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CHECK YOUR GOT-drat PINOUTS I slaved all weekend on a bipolar linear supply and a TL082 preamp because I was sick of rigging up divider networks, and assumed that 78xx and 79xx regulators had the same pinout. WRONG-O. Evidently I blew my 7915 because even after rewiring correctly I'm only getting -3.1v when the unregulated rail is -18, -19 volts or so. My lone 7915. My lone 79xx at all. And the best part is that Rat Shack doesn't carry any 79xx regs and I'm moving in a week, so I don't have the occasion to get one. single. regulator mailed to me. ARGH. On the bright side, I did successfully mask and etch my own power supply PCB and hell, I more or less built a linear supply. First thing I've done that uses 120 directly. I'm stoked, little bit of heatshrink and attention and it's safe as houses. Edit2: Comedy regulator time. I found 15 volt zeners in my box so I'm going to use those to bias a 2n2222a/2n2907 pass transistor pair. 14.5ish volts should work fine for the preamp. I want to see if I can get this poo poo moving, haha. Figuring 4-6v of drop across the transistors with max current of 30 mA absolute tops, quarter watt of power dissipated in each at the most. The power LED's draw more juice than the amp in this circuit, almost. Jonny 290 fucked around with this message at 19:48 on Jun 15, 2008 |
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Jun 15, 2008 17:31
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It lives! Instead of linear regs I just pulled out a 2n2222a/2n2907 pair and ran them as emitter followers, using 15v Zeners biased at 10 mA-ish for the base drive. Voltage looks great, 14.32 or so on either rail. Wired it all up and scratched my head until I finally realized that I never connected the inverting input back to the gain network. GAH. Wired it up and the whole thing sprung to life. Great gain, low noise, I'm happy. It's all crammed in a Radio Shack aluminum box so there's a teensy bit of PS hum, but what can you expect for a first power supply, heh. Edit: Further question: On my supply I used a 3 prong cord, used hot/neutral and heatshrinked the ground wire inside the supply, so it's currently disconnected. My PS has a metal case, and the secondary center tap connected to ground. Is it a good idea for me to connect the AC ground to chassis ground? Do I want to maybe put in a ground lift switch to counteract possible ground loop issues (which don't exist in my studio, but may in the field)? Jonny 290 fucked around with this message at 22:25 on Jun 16, 2008 |
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Jun 16, 2008 16:17
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Three-Phase posted:So what's he currently working on? Small signal stuff is neat but I think that working with high current and/or voltage is an interesting and worthy challenge. It's one of the main reasons that I am investigating converting a crotch rocket to electric - I want to build the motor controller myself. Something about PWM'ing 80 amps at 48 volts makes me RRRRRR.
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Jun 17, 2008 15:17
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Either I'd get a standard solar charge controller, maybe look for one that adjusts down to 9.6v, or I'd reconsider the sealed lead acid battery in the system. It's cheap, 20 bucks for a 7 amp hour and about 40 bucks for a 20 amp hour. $300 is way more than you actually need to pay.
Jonny 290 fucked around with this message at 04:34 on Jun 18, 2008 |
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Jun 18, 2008 04:31
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Those waves do not have a voltage or current, but they will induce a voltage or current as they pass through a conductor. For what it's worth the average level of a signal needed for clear FM reception (what FM radio, police radios, etc) is around 0.16 uV. Field strengths are measured in 'microvolts per meter'. Also, the Darlington doesn't have much to it. At the cellular frequency range you are generaly using FET transistors or more likely MMIC's (monolithic microwave integrated circuits) which are a relatively new tech, bascially an easy to use amplifier block in one chip. Very high frequency and microwave tech is hard to engineer and build, and MMIC's make a lot of commodity situations much simpler.
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Jun 19, 2008 16:30
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After you solder some traces, you can hit them with fingernail polish for some two-cent insulation. I wouldn't cross traces in direct contact with just nail polish protecting but it helps avoid those "whoops chassis too small, shorted all my parts out" situations. And yeah, I just solder 'paths' with the component leads. Make sure the component leads have good contact to one another, don't rely on solder blobs to carry the juice.
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Aug 13, 2008 22:22
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God drat I had exclusive access to not only an AT&T T1 but a 20/5 cable line and still couldn't get through (i restricted myself to two browser tabs refreshing at any one time). Still, it was fun to try. I still want to buy some microcontroller type stuff and learn on it, it just will have to wait a while =/
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Jan 7, 2010 20:01
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I have a project that I want to undertake, and the biggest part of it is a laptop and some sort of hardware interface. What I need is 4-8 digital outputs, a couple 5v analog ins (low frequency is fine, just sensor reading) and 4-8 digital ins. I'd like a couple PWM channels too but it's not a necessity at all. Should I just use a low end Arduino and write a program to access/set the hardware lines? Any other simpler suggestions?
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Apr 26, 2011 05:07
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Well, I don't know any C other than "the two weeks I took in college in 1997", but that's no reason to stop. I just want to use it as a serial interface so I can use Python to actually r/w the values and set pins. Not really interested in comprehensively learning C at this point in my life, though, but the basics to use them as i/o look easy.
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Apr 26, 2011 21:20
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Wait,am I reading this right? This is the bread and butter of an Uno at a much lower price? Hot drat, I may have to read up on this poo poo some more. That is much more reasonable considering that I already have breadboards and poo poo.
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Apr 27, 2011 04:27
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Thanks, dudes! I'm going to flip a spare laptop for a $100 Arduino slush fund. I can't wait to goof off with these things - man, I wish they were around when I was a kid.
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Apr 27, 2011 16:16
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So, one problem I have with circuitry is that I can't think of ideas. I finally have one. I have a couple of Icom PCR-100 serial-controlled receivers and am not doing anything with either. Going to get an Arduino and use a 16x2 LCD along with some supporting parts to build a controller for it. It won't be that wiring-intensive, really. Stage 2 will have me doing the same thing, but in a gutted antique radio chassis (I'll pick a dead one, don't worry) with Nixie display and IR remote, and perhaps even a low-watt tube audio amplifier. It'll be pretty cool to eventually have an Olde Tyme Radio that can do everything from listen to local AM nutjobs to far-off shortwave to the local cops, with a billion memories and modern stability.
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Jun 23, 2011 21:37
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I'm really excited. Money has been tight for a couple of years, and I have had to lay the iron down for a while. But yesterday when I was at Radio shack buying thermal paste for a GPU reflow project, I was reminded that they carry Arduino stuff now. Picked up an Uno and have successfully annoyed the wife with blinking LED's and speaker beeps already. These things are a ton of fun! I have a Big Project That I've Wanted To Do in the back of my head, and now I can get started. I am going to take one of my spare Icom PCR-100 receivers (it's basically a wideband radio controlled via serial) and build a 44780LCD + couple-of-buttons interface to it. Just something proof of concept to tune around and mute it and maybe put a couple of presets in. The final phase will be to put Arduino + Icom into a stripped and finished vintage radio cabinet, do a Nixie frequency display and add IR remote, replace a couple of the knobs with rotary encoders for tuning and volume. Modern radio tech in old package, more or less.
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Jan 14, 2012 08:42
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Yeah, I'll be using a Teensy or something similar when I build the final product. I'm not going to invest the time in building up the whole AVR circuit side from scratch for this project - it's more efficient for me to just buy a board and wire it up - but this was just a fun instant-gratification surprise to kind of motivate me a bit.
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Jan 14, 2012 09:15
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I've got this Icom PCR-100 that I have wanted to hack on for a while. I added a 10.7 MHz IF out a while back, but wanted to rig it up to be controlled by something other than a PC, as the software out there is terrible, and I figured if I'm going to write software I'm going to do a hardware UI as well. It has a proprietary but documented serial control protocol, just hook up at 9600 and go. I dug up the command spec and schematics and started looking. First problem was that it has a real RS-232 in, whereas my Uno only has TTL. I reasoned that nothing really speaks RS232 levels internally, so I started looking for a level converter chip on the radio, and found it. After finding the datasheet for that, it appeared to have an enable pin that when high would cause the chip to convert RS232 to TTL, and when low would float all the ins and outs. Found the line from the CPU to the enable pin on the converter, as well as the TX and RX pins, and lifted a side of the diode that provided the high signal. From there it was easy to tack two wires on to the CPU pins, bring them out and wire it up. Now that I have that part done, I have enough code written that the radio is turning on, setting volume and tuning to a station. The rest is just UI and writing the program. I'd like to find a decent quality rotary encoder without detents, and would love any suggestions for what to look for. It doesn't have to have a very fine resolution, but my ultimate plan is to retrofit all of this into an old radio and a clicky tuning knob wouldn't feel right. It can come with or without a push function, doesn't really matter.
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Jan 29, 2012 23:58
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Are you trying to equip a real lab that is going to want some sort of semblance of professionalism? Or is this just for giggles? If it's for a hobby workbench, I would take a look at ripping apart a $10 drafting style lamp from Walmart, or something like that.
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Feb 2, 2012 13:24
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taqueso posted:There are ICs that take BCD input and drive a 7-segment LED. They are not very popular anymore, of course. You could use a counter IC that is controlled by pushbuttons and the BCD->7seg IC to make a simple counter. Cost and complexity is going to approach arduino pretty fast, though. Besides my obvious enjoyment of this picture, I also wanted to mention thumbwheel switches, they were extremely popular for years and are rock solid. Plus you can kind of get a retro/industrial/Fallout vibe going on for the box design.
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Feb 3, 2012 10:55
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Triikan posted:Can somebody explain wall warts to me? I just switched my network around a bit, and realized I've been running my main router for about a year on a 12v power supply when the router says it needs 5v. Router always ran a bit hot, but was rock stable. Why did this work and not destroy my router? As mentioned above, but in a bit more detail: The first device inside your router's power chain is probably a simple linear voltage regulator. More or less, this takes "whatever comes in on the input", gives X volts on the output (5 for a 7805 for example), and gets rid of the difference as heat. So, say your router truly runs off 5 volts and your wart was putting out 6 (this is common, warts usually sit a few volts high). If your router was drawing one amp of current, the voltage regulator would have to get rid of ((6 - 5) * 1) = 1 watt of power. If, however, your wall wart was giving off 14V (about average for 12V warts), that same chip had to dissipate (14 - 5) * 1) = 9 watts of heat, much much higher. Many devices are starting to use switching regulators however, which can convert power more efficiently into a desired voltage/current and do not just shunt off the excess as thermal energy.
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Feb 14, 2012 09:54
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Eh, just keep an 0.5A fast-blow in line with the AC and keep a hand in your pocket when twiddling. You guys would back away slowly from the '53 Silvertone two-tube combo under my bench. All of the cloth wiring's insulation is mostly gone inside. Bare wires errywhere (assuming ~250V for the plates, haven't ever metered this amp out to be honest). Still works, too, with the exception of a bypassed volume control. I have no idea how those caps have not shorted. 6K6's are a weird choice, for sure. Jonny 290 fucked around with this message at 09:12 on Feb 18, 2012 |
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Feb 18, 2012 09:09
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Yeah, let's talk surplus gear, please. I'm about to get a bonus from work and can finally drop a couple hundo on test gear. I want a scope, signal gen and bench DMM in that order. I think I was narrowing it down to Tek 2213's or 2215's. Any opinions on good/bad models? I can't spend more than $100 per piece of gear, really. I will be wanting to work with <30 MHz RF stuff eventually, to start out I'll just be playing with audio amps.
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Mar 21, 2012 11:53
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TacoHavoc posted:I have a BK precision 2125B scope and a BK 2005B RF signal generator I could sell. I got them from an older audio engineer that was cleaning out his basement, and I don't really have a use for them. If either of those are interesting to you let me know. Hey cool, jonny290 at gmail dot com, if you don't mind. The bench meter is just an aesthetic thing and for ease of use, really. Bench space is absolutely not a concern; I have many square feet of shelves to fill up and want to get a nice looking test bench to go next to the radio desk. I have an Amprobe handheld DMM that works very well, for sure, I would like a second DMM though for flexibility. Maybe just get another handheld?
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Mar 22, 2012 08:38
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I am conscious and wary of the deadly effects of high voltage and will exercise all proper work habits when touching this thing. OK beards, dig deep. I picked up a mid-sixties all tube AM/FM/record player stereo console from the flea market today. AM is fine and strong, and the turntable, as skate and skiptastic as it is, sounds great, but we have really low volume on FM. If you dime the volume, you get a 50/50 mix of hum and music at very low volume, like, if the air conditioner kicks in it's gone. Output is a pair of 6L6's so there should be excessive power available, and Rush Limbaugh rattled the windows earlier, so the finals are good. We're tuning around fine, the sensitivity is okay and it's picking up the stations I expect it to. What would you look at? FM side tubes? Coupling caps? Switch? Audio tracing tube radios sketches me out. I'm assuming I should put a billion volts of blocking cap in line with any audio tracer. I don't think it's a bad switch contact, or any of the FM front end or IF tubes, but I could be wrong. It's a JC Penney "Two Sixty" and I'm sure it was just a commodity item, so I am not expecting a schematic, but there is a tube diagram on the chassis, so I at least have a toehold. Jonny 290 fucked around with this message at 23:37 on May 15, 2012 |
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May 15, 2012 23:34
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Hidden Under a Hat posted:Could y'all clarify something for me? With PWM control of LEDs, are the LEDs actually flashing super fast (would high-speed photography catch an LED in an off state) Correct, and this is actually becoming a big issue for automotive photography. A lot of the trim and marker lights on new cars are now LEDs which are PWM driven, and often they appear off or partially out in photos as they're being caught during an off cycle.
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Jun 7, 2012 08:54
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