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It'll start up in the same state that it was shut off in. Assuming ideal conditions.
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Apr 5, 2010 23:52
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According to http://www.cybermike.net/reference/liec_book/Digital/DIGI_10.htmlquote:The astute observer will note that the initial power-up condition of either the gate or ladder variety of S-R latch is such that both gates (coils) start in the de-energized mode. As such, one would expect that the circuit will start up in an invalid condition, with both Q and not-Q outputs being in the same state. Actually, this is true! However, the invalid condition is unstable with both S and R inputs inactive, and the circuit will quickly stabilize in either the set or reset condition because one gate (or relay) is bound to react a little faster than the other. If both gates (or coils) were precisely identical, they would oscillate between high and low like an astable multivibrator upon power-up without ever reaching a point of stability! Fortunately for cases like this, such a precise match of components is a rare possibility. 
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Apr 5, 2010 23:57
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^ What he said, if you've got a stable startup race condition that you would like to make use of, then you can simply elect to use the output of the other gate as 'true', and change the switches. Alternately, you can put an RC filter with a time constant of something like 10 uS on the output of one of the gates, which should allow you to adjust which stable state is reached first. This will be more consistent over time. code:
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Apr 6, 2010 02:33
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Delta-Wye posted:Maybe switch the gates? When I was testing the circuit I was using a logic probe instead of an LED. With the LED attached it works fine. If I powered the circuit with the logic probe on the pin, it would show HI instead. I learned my lesson... sometimes LED's are better then logic probes.
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Apr 6, 2010 02:38
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You didn't have a 'problem'; there are no privileged logic states of that circuit, except as arbitrarily defined by you, either one gate dominates or the other. By loading the output of one of the gates, you slightly altered the transient behaviour and contributed to one of the gates taking precedence during the startup sequence.
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Apr 6, 2010 04:08
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Hello I have an idea, that I'd like an informed opinion on. I'm an emerging coffee/espresso nerd. I've already modified my espresso machine with PID temperature control, and now it's the grinder's turn. My grinder is dumb as a box of rocks. One switch, one electric AC motor, that's it. Fancier, more expensive grinders have timers, so you set a given grind time (8.3 seconds, for instance), and you just push a button once, and the grinder runs for the specified duration. This results in the same amount of coffee for your espresso every time, which is desirable. I'd like to modify my grinder to do the same. Does a component exist, that: Runs on 230VAC only (12V or 24V is doable, but less desirable) Let's me adjust the delay Will close a relay (SSR maybe) for, say, ten seconds after a quick press of a button. I think the power draw is around 300-400W. Apologies if this is more of an "electrician" question and less of an "electronics" question.
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Apr 6, 2010 14:21
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bolind posted:Hello You can get adjustable time-delay relays. They are commonly found in elevator systems. However, they're expensive, and you can save a lot of money building something like this: http://www.aaroncake.net/circuits/relaytim.asp Note that the 555 is not very precise for long time delays, so it may not give you exactly the results you are looking for. It's cheap though, so it's probably worth trying. Also you'll need to make sure your relay draws less than 200mA, which should be easy enough.
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Apr 6, 2010 16:54
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Instead of a relay you could also use a transistor and a triac and go the solid state route. The 555 should work fine for you coffee grinder needs. You will need to build a small power supply circuit unless you want to use batteries.
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Apr 6, 2010 17:32
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dv6speed posted:Instead of a relay you could also use a transistor and a triac and go the solid state route. The 555 should work fine for you coffee grinder needs. You will need to build a small power supply circuit unless you want to use batteries. You should probably use an optocoupler instead of a transistor to control the triac so you keep 120V out of your low-voltage stuff, but otherwise, yeah, that's good advice. e: You'll need one with a triac output, something like this: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=160-1372-5-ND Mill Town fucked around with this message at 00:11 on Apr 7, 2010 |
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Apr 7, 2010 00:04
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ANIME AKBAR posted:So I've built my daughtercard for the de0 cyclone III dev board, and I'm testing it out and things are going well. However, when I was testing some code for interfacing with some quadrature encoders, I noticed that some of the user LEDs on the de0 board were blinking. They are, according to documentation, driven directly by the FPGA, but in my design I am not using those pins. So I tried tying those pins low in my design. Now those LEDs stay off, but a few other LEDs are blinking in a similar way. The blinking is definitely related to my program, (like one of them blinks every 16 encoder counts, another every 128). My best guess is you (or more likely your compiler, vis: quartusII) have just met or are unknowingly utilizing (overoptimizing upon) the 'Multitrack Interconnect' "feature". http://www.altera.com/literature/hb/cyc3/cyc3_ciii51003.pdf http://www.google.com/search?hl=en&rlz=1G1GGLQ_ENUS356&q=cyclone+3+multitrack+interconnect&aq=f&aqi=&aql=&oq=&gs_rfai= Whompy fucked around with this message at 03:03 on Apr 7, 2010 |
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Apr 7, 2010 02:54
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Mill Town posted:You can get adjustable time-delay relays. They are commonly found in elevator systems. dv6speed posted:Instead of a relay you could also use a transistor and a triac and go the solid state route. The 555 should work fine for you coffee grinder needs. You will need to build a small power supply circuit unless you want to use batteries. I'm ready to drop up to $100 for an industrial-type turnkey solution. If possible, I'd like to avoid DC and soldering and all that, but if it's necessary then... The delays needed are probably in the 2-20 second range, with a resolution no finer than 0.1 second, and even half a sec would probably be fine. I looked at RS online, and they had a bunch of delay profiles. Most of them started the timer after the release of the button, but put the signal high at the press. So your total running time for the grinder would be the time the button was pressed + the constant delay, and since I can't guarantee the same press every time, things will be inaccurate. Is there a button that only gives a fixed "burst" of contact?
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Apr 7, 2010 07:59
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bolind posted:I'm ready to drop up to $100 for an industrial-type turnkey solution. If possible, I'd like to avoid DC and soldering and all that, but if it's necessary then... I'm sure in the 50's they would have built a resistor/capacitor circuit to accomplish that... which would take up more space and be more complicated then a DC driven 555 timer circuit. My advice would be to build a box that has it's own power cord, and has an outlet to plug the coffee grinder into. You can tuck away the adjustment knob, DC power supply, 555, and your triacs or relay in there and have a relativily small self contained unit. Building it in this way would allow you to use the timer with other coffee grinders, or any other AC powered device that you want to only use for 2-20 seconds at a time. Edit: It's an old design that uses a timer from Radio Shack that I'm sure is now obsolete, but I built this pretty cool circuit from a Popular Electronics article in the mid-late 90's called the "Time-off". You can set the timer anywhere from a couple seconds to hours and have it turn the device off when the timer rings. It would work perfectly for your needs, and give you more accuracy then you require, but I doubt you'll want to build it, even tho it's an awesome device. AbsentMindedWelder fucked around with this message at 12:49 on Apr 7, 2010 |
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Apr 7, 2010 12:43
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Need a little help in finding a transformer. Some time ago I bought a used chinese-made 6-channel powered mixer, and it's missing its transformer. Looking at the components, I noticed that the transformer needs two outputs, and it also has to be center-tapped (the rectifiers only use two diodes each). And looking at the caps near the diodes, I'm guessing that the voltages after the rectifiers are 24v and 48v (as the caps have a max voltage of 25v and 50v). The amplifier itself looks to be a class B flavor, and the mixer has both balanced and unbalanced mic inputs, so that also means it can also supply phantom power (though it's anyones guess if it actually gives the required +48v to the mics). I tried googling, but couldn't find anything that would fit these criteria. [Edit] And I live in northern Europe, so 230v input is needed. [Edit2] Derp, power requirement would be nice  It does have a 3 amp fuse for the mains, and it's advertising "300W Full Power Audio" on the front.
JointHorse fucked around with this message at 16:40 on Apr 9, 2010 |
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Apr 7, 2010 19:09
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Whompy posted:My best guess is you (or more likely your compiler, vis: quartusII) have just met or are unknowingly utilizing (overoptimizing upon) the 'Multitrack Interconnect' "feature". I posed the same question on the altera forums, and got a snarky reply from an admin that any output ports defined in your top level file will be assigned to pins, whether or not they were done explicitly in the pin planner. I normally have a few ports in my design that are only there for the sake of simulation, and aren't pinned out manually, so they were being randomly assigned pins during compilation. I still have no idea why this is the case or how to prevent it, and was pretty much told to deal with it by the admin. Anyways, removing the extra ports in my design appeared to solve the issue, but it's a pain in the rear end to have to add and remove ports every time I want to simulate. As for this multitrack interconnect feature, I searched through those documents for the term but couldn't find anything that suggests it's related to my problem. I'm pretty sure it's an issue with quartus, not the device itself.
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Apr 8, 2010 14:55
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ANIME AKBAR posted:I posed the same question on the altera forums, and got a snarky reply from an admin that any output ports defined in your top level file will be assigned to pins, whether or not they were done explicitly in the pin planner. I normally have a few ports in my design that are only there for the sake of simulation, and aren't pinned out manually, so they were being randomly assigned pins during compilation. I still have no idea why this is the case or how to prevent it, and was pretty much told to deal with it by the admin. Anyways, removing the extra ports in my design appeared to solve the issue, but it's a pain in the rear end to have to add and remove ports every time I want to simulate. If you look through the Cyclone III Device Handbook (Vol I & II, Included in the CDROM of the DEO board) you'll come across this gem: Handbook posted:MultiTrack Interconnect ...Which says to me that when you added those extra ports the software (or the device itself) assumed that they were to be used, somewhere, and basically said "poo poo, This bit isn't connected to anything? Goddammit...I'll just hook it up to this pin over here and hope for the best..." <edit> I took a second look and the link in the handbook is wrong: instead just scroll down to page 41 where it describes it's auto-routing magic... Whompy fucked around with this message at 16:25 on Apr 8, 2010 |
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Apr 8, 2010 16:11
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ANIME AKBAR posted:I posed the same question on the altera forums, and got a snarky reply from an admin that any output ports defined in your top level file will be assigned to pins, whether or not they were done explicitly in the pin planner. I normally have a few ports in my design that are only there for the sake of simulation, and aren't pinned out manually, so they were being randomly assigned pins during compilation. I still have no idea why this is the case or how to prevent it, and was pretty much told to deal with it by the admin. Anyways, removing the extra ports in my design appeared to solve the issue, but it's a pain in the rear end to have to add and remove ports every time I want to simulate. I'm assuming by simulation you mean the waveform viewer? You can prevent this "problem" by not assigning ports (which get mapped to pins on the device either explicitly by you, or implicitly by the compiler) to internal signal nets, and instead, naming your internal nets something other than "wire000001" or whatever they default to. These internal signals can all be accessed from within the waveform viewer. When you add signals it defaults to a filter of "pins: all" but you can change it to show nets/registers/etc. It's not a problem in Quartus, there's a difference between what you're telling the software to do, and what you want the software to do. Edit: had some terminology mixed up. Chalupa Joe fucked around with this message at 04:43 on Apr 9, 2010 |
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Apr 9, 2010 04:30
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I have a somewhat large transformer that came out of an old APC battery backup. Its original function was, I presume, to take 24V from the batteries and convert it to the 120V needed to operate whatever was plugged into it. Would it be kosher to run the transformer in the reverse direction - give it 120VAC, and rectify/regulate the 24V output to create a nice high amperage 24VDC (or variable) power supply? I'm trying to educate myself, but I don't know if this is a safe project to pursue any further.
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Apr 11, 2010 00:07
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It might be. Hook the HV side up to a low-voltage AC source and measure the actual open-circuit transformer ratio. That will tell you what voltage you might be able to get out of it. Measure the magnetising inductance at the high-voltage side. It needs to be high enough to avoid a large magnetising current draw when connected to the mains.
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Apr 11, 2010 00:30
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I have a theoretical question. Say you have something that works at DC 12v and your power source is an unknown unfiltered 12v OR 24v system. How could you implement something that would spit out a clean 12v that did not require the operator to switch a toggle, etc according to if 12 or 24v was fed into the system. Another possibly more complex example of this would be a circuit that say.. required DC 5v and whose power supply would spit out between 5-9v. You couldn't use a regulator because there would be an unacceptable drop. I guess you could step up the voltage and then regulate that to the 5v, but that seems rather inefficient. edit: wow, is it as simple as just using a switching regulator? macpod fucked around with this message at 03:54 on Apr 11, 2010 |
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Apr 11, 2010 03:47
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Acid Reflux posted:I have a somewhat large transformer that came out of an old APC battery backup. Its original function was, I presume, to take 24V from the batteries and convert it to the 120V needed to operate whatever was plugged into it. Yep feel free to use the transformer in any direction. Just don't exceed its VA rating.
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Apr 11, 2010 04:26
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macpod posted:edit: wow, is it as simple as just using a switching regulator?
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Apr 11, 2010 04:54
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I'm trying to convert an old deep fryer into a temperature controlled water bath for sous-vide cooking. I'm not looking for an elusive 0.1°C precision in a 8 liter water bath, despite what people selling DIY kits for this cooking technique are saying. Would one of the following kits be a good start for this ? http://www.velleman.eu/distributor/products/view/?id=9296 http://www.velleman.eu/distributor/products/view/?id=9094 Then I need to interface this with a relay to be able to switch off the heating element. The same website has a lot of relays, how do I choose one ?
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Apr 11, 2010 13:21
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Acid Reflux posted:I have a somewhat large transformer that came out of an old APC battery backup. Its original function was, I presume, to take 24V from the batteries and convert it to the 120V needed to operate whatever was plugged into it. What unit did you get it out of? Not all of those run on 24V batteries.
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Apr 11, 2010 13:55
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Hillridge posted:What unit did you get it out of? Not all of those run on 24V batteries. I'm going to follow catbread's advise about low voltage AC testing when I'm back at work on Tuesday. We have a variable AC power supply in the shop that I rarely have occasion to use for anything else, so this'll be a good opportunity to dust it off and run it for a while.
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Apr 11, 2010 19:09
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Anyone have a decent resource for DIY mains transformers? Or a source for samples? I'd like to make something around 100W stepping from 120V AC down to 3 taps of 40v, 20v, 10v. Or maybe more if I'm making it. Haven't actually done the math yet. I don't really wind coils much and the last time I did it was years ago. That coil was 2KW, shook, smoked and buzzed angrily. Also if you didn't pay attention it would simultaneously burn and shock you. Mostly I just want to make an over engineered transformer that will be safe. ValhallaSmith fucked around with this message at 18:27 on Apr 12, 2010 |
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Apr 12, 2010 09:57
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ValhallaSmith posted:Anyone have a decent resource for DIY mains transformers? Or a source for samples? I'd like to make something around 100W stepping from 120V AC down to 3 taps of 40v, 20v, 10v. Or maybe more if I'm making it. Haven't actually done the math yet. I just made one in my project thread. It offers 220vdc,110vdc,80vdc,12vdc,and 5vdc with a couple safe guards. I got my inspiration from this guys website: http://www.mcamafia.de/nixie/ncp_en/ncp.htm You can buy safe transformers these days from mouser or digikey.com. Just make sure its rated at what whatever VA rating to accommodate that much power.
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Apr 12, 2010 20:24
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I hope someone here can help me with a project I'm working on. Basically I am setting up a system that runs off of 12v DC power (from an automobile power outlet) that needs to power one LED and this solenoid valve. I will be using a simple on/off switch from radioshack. I am quite sure this is pretty simple, but I don't really know where to begin, but I have a feeling that if I just wire something up and go, I'll end up burning the car down. I've already started by reading the basics, but can someone here take a crack at walking me through this? If I just connect everything together (power > switch > LED > valve > power) is this going to work and be safe?
JesusDoesVegas fucked around with this message at 04:27 on Apr 16, 2010 |
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Apr 16, 2010 04:18
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 The valve looks like it's just a switch that opens when you give it 12V. The resistor value is (12v - led forward voltage) / (some safe current for the resistor, 20mA is a good choice). Eg. 1.6v forward voltage: 520Ohm Resistor Scarboy fucked around with this message at 04:55 on Apr 16, 2010 |
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Apr 16, 2010 04:51
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Scarboy posted:The valve looks like it just a switch that opens when you give it 12V. A solenoid valve is basically like a relay, but for fluids. This particular one is the equivalent of SPDT.
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Apr 16, 2010 04:55
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wow. Thank you. Did not expect a schematic and everything. I'll post back here when I get it running. edit - Miltown: does the above schematic still apply?
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Apr 16, 2010 04:58
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Yeah
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Apr 16, 2010 05:49
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JesusDoesVegas posted:does the above schematic still apply? If you are running this from an already existing, previously fused circuit, then don't worry about it.
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Apr 16, 2010 13:08
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Like one of the fuses that a car has?
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Apr 16, 2010 20:45
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ante posted:Like one of the fuses that a car has?
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Apr 16, 2010 21:59
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dv6speed posted:Hey, for all we know, he had plans of wrapping a bare copper wire around the battery terminal. The thought had crossed my mind.
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Apr 17, 2010 07:32
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I thought it would be a neat project to build a hot cathode electron gun like the one described on this page. Has anyone built one before? Are there are any safety hazards beyond the standard wall power precautions? What are some suggestions for the design and materials? Edit: I am mainly concerned with the tube itself building up a deadly charge. I know CRTs build up big charges but I'm not sure if that's the tube itself or the capacitors in the circuit. None of the home-made electron gun sites I've found mention it either way. BattleMaster fucked around with this message at 17:44 on Apr 19, 2010 |
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Apr 19, 2010 03:48
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I need to get a udn2597a sink driver and everywhere I call has a minimum order of a couple hundred bucks. I've checked out the places in the OP with no luck. Can anyone give me a place to check out?
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Apr 19, 2010 19:22
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Jihad Me At Hello posted:I need to get a udn2597a sink driver and everywhere I call has a minimum order of a couple hundred bucks. I've checked out the places in the OP with no luck. Can anyone give me a place to check out? It depends on how long it's been discontinued, but I doubt you will find any place that would sell small quantities. Can you find another part that would substitute?
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Apr 19, 2010 21:32
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Actually found it on Ebay.. coming from Hong Kong.. we'll see.
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Apr 19, 2010 22:28
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BattleMaster posted:I thought it would be a neat project to build a hot cathode electron gun like the one described on this page. Has anyone built one before? Are there are any safety hazards beyond the standard wall power precautions? What are some suggestions for the design and materials? Production of x-rays I'd say would be your biggest concern. I'm not sure either if the charge warnings come about as a result of the tube or caps used in the circuitry.
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Apr 20, 2010 04:14
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