Electrical Engineering V3 - Developers

Hell yeah. if I wanted to be really authentic I'd modify it for 20ma current loop for the teletype machine. Now I have to begin looking into disk and tape. Recently people began designing USB interfaces for the peripherals that were compatible with SIMH which this replica runs. In theory I can run this baby with a TU56 and an RL02 and save myself at least $5000. I should have a dismantled half rack buried around back to put everything in.

Ddrl and I are trying to figure out is this site is for real or not. [url]http://mail.blockyourid.com/~gbpprorg/mil/[/url] It reads out like the guy is completely insane or so- [quote]Al-Jazeera Satellite Reception Jammer Device to jam Al-Jazeera propaganda broadcasts Status: Complete [/quote] [quote]Fox News Rebroadcaster Portable over-the-air television station to rebroadcast a cable TV signal Status: Complete [/quote] oh.

[url]http://www.irf.com/product-info/datasheets/data/irf4905pbf.pdf[/url] [url]http://www.irf.com/product-info/datasheets/data/irf3205.pdf[/url] Okay so i bought 24 IRF4905PBF's ($1 USD for 2) and 12 IRF3205's ($1 USD for 1) I think that should be enough to build 3 H-bridges

[QUOTE=cartman300;48560682][url]http://www.irf.com/product-info/datasheets/data/irf4905pbf.pdf[/url] [url]http://www.irf.com/product-info/datasheets/data/irf3205.pdf[/url] Okay so i bought 24 IRF4905PBF's ($1 USD for 2) and 12 IRF3205's ($1 USD for 1) I think that should be enough to build 3 H-bridges[/QUOTE] Did you get those IRF4905BPFs from ebay? Find it hard to believe that price since they're quite a bit more expensive at the real distributors, even in large quantities: [url]http://www.digikey.com/product-search/en?keywords=IRF4905PBF[/url], [url]http://www.newark.com/international-rectifier/irf4905pbf/p-channel-mosfet-55v-74a-to-220ab/dp/63J7300?ost=IRF4905PBF[/url]. Might not matter in your case, but they might be fakes.

[QUOTE=ddrl46;48560875]Did you get those IRF4905BPFs from ebay? Find it hard to believe that price since they're quite a bit more expensive at the real distributors, even in large quantities: [url]http://www.digikey.com/product-search/en?keywords=IRF4905PBF[/url], [url]http://www.newark.com/international-rectifier/irf4905pbf/p-channel-mosfet-55v-74a-to-220ab/dp/63J7300?ost=IRF4905PBF[/url]. Might not matter in your case, but they might be fakes.[/QUOTE] Yes i did buy them on ebay, that's why i also bought ones that can withstand much more power than i'm actually going to supply. The ones somebody mentioned on the last page were too expensive (90€ shipping) so that's definitely my only solution.

So why did you get 24 of one and 12 of other?

[QUOTE=Fourier;48561191]So why did you get 24 of one and 12 of other?[/QUOTE] Bought 12 of each, it just so happens they pack 2 IRF4905PBF's in one pack for the same price.

Hopefully have a fun project coming up. My dorm in college has a music room with a 1960's Hammond M-100 organ that barely works at all. It sounds like it's probably never been oiled and most likely has barely been used since it was put there in the 70's. My plan it to get permission to open it up, check all the tonewheels and all the caps and replace anything that can be replaced economically (these organs used wax film caps so I'm going to guess they need to be replaced) Should be fun and hopefully I can get it up and running without having to spend a significant amount of money (odds are I'll just stop if it ends up being too much)

[QUOTE=papkee;48562851]Hopefully have a fun project coming up. My dorm in college has a music room with a 1960's Hammond M-100 organ that barely works at all. It sounds like it's probably never been oiled and most likely has barely been used since it was put there in the 70's. My plan it to get permission to open it up, check all the tonewheels and all the caps and replace anything that can be replaced economically (these organs used wax film caps so I'm going to guess they need to be replaced) Should be fun and hopefully I can get it up and running without having to spend a significant amount of money (odds are I'll just stop if it ends up being too much)[/QUOTE] Ooooh, sounds like fun. Post pics of the inside. The JD-XA site from Roland had a cutaway of the inside of the synth showing the two halves (analog/digital) and it was really neat. Almost makes me want to crack open its little brother the Xi when mine arrives in the mail merely just so I can see the inside and look at it.

My synthesizer project has rapidly evolved (or maybe devolved...) into something much bigger than originally planned. For the Digital part I wondered if I could keep the CPU and audio output circuity in a SO DIMM plug so that it could be swapped out if you wanted more polyphony or better output or something. Also thinking trying to get a Rasp Pi, one of the very first models off the assembly line, to power and run the digital portion. And maybe be able to monitor the analog seciton and send CV/gate signals to it from converted midi signals. Which would mean playback and sequencing abilities. Maybe add a touch screen for more control of digital portion and analog sequencing but hell then I have to program things and I suck at programming. [editline]29th August 2015[/editline] I have used this to learn a new and improved circuit CAD software, DipTrace. has been nice so far. 3d pcb view is really neat. Have a basic vco design so far, as practice for this software.

Today I found and immediately joined my school's Radio Club. They have fun toys. [t]http://i.imgur.com/RzvaxOL.jpg[/t] [t]http://i.imgur.com/OZ5ZXcT.jpg[/t] [t]http://i.imgur.com/BfZiNaN.jpg[/t]

[QUOTE=papkee;48572463]Today I found and immediately joined my school's Radio Club. They have fun toys. [t]http://i.imgur.com/RzvaxOL.jpg[/t] [t]http://i.imgur.com/OZ5ZXcT.jpg[/t] [t]http://i.imgur.com/BfZiNaN.jpg[/t][/QUOTE] I want a picture of your HF beam(s). Also is that Motorola XPR6550 your only DMR unit? Edit: [url=https://i.imgur.com/3W1f6lo.jpg]My station, not as many fun toys.[/url] And this was all because someone in this thread bought an RTLSDR and I thought that was cool.

Finished first ever schematic. Slight modification of pre-existing schematic. Any guesses what it does? [t]http://i.imgur.com/W4CYNn8.png[/t] [sp]Pretty easy but yes just two parameter attack/release volume envelope shaper. I think I could make it snappier by adding a cap in parallel with the feedback resistor near the amp at the bottom. Which means lowest attack time could be really really low. Also need to finish my first general fun design so I can order some components and test the PCB mill nearby.[/sp] Also the way white noise made is fascinating, had no idea it was so innovative. Thought it would require a special chip but nope lets abuse this transistor a bit and get truly random white noise

[QUOTE=Cakebatyr;48573557]I want a picture of your HF beam(s). Also is that Motorola XPR6550 your only DMR unit? Edit: [url=https://i.imgur.com/3W1f6lo.jpg]My station, not as many fun toys.[/url] And this was all because someone in this thread bought an RTLSDR and I thought that was cool.[/QUOTE] The beams are in another building entirely and I can't get up there since apparently only school employees can go on roofs. A few of the guys have DMR radios, that was one of them. We just set up a DMR repeater and it's now the second most popular in the state. Unfortunately I am too poor to afford a proper DMR radio. I'm going back today just so I can play with that spectrum analyzer and frequency generator.

Looking for a bit of advice, I recently bought a MPU-6050 (link at bottom) and whilst I was soldering the headers on I noticed the board got quite hot - is this normal and doesn't this risk damaging the chip on the board? If so what can I do to mitigate the risk? MPU-6050: [url]www.amazon.co.uk/gp/aw/d/B00COD97LY/ref=mp_s_a_1_1?qid=1440986297&sr=8-1&pi=SY200_QL40&keywords=mpu-6050&dpPl=1&dpID=41-gLq5SqJL&ref=plSrch[/url]

[QUOTE=Dorkslayz;48578520]Looking for a bit of advice, I recently bought a MPU-6050 (link at bottom) and whilst I was soldering the headers on I noticed the board got quite hot - is this normal and doesn't this risk damaging the chip on the board? If so what can I do to mitigate the risk? MPU-6050: [url]www.amazon.co.uk/gp/aw/d/B00COD97LY/ref=mp_s_a_1_1?qid=1440986297&sr=8-1&pi=SY200_QL40&keywords=mpu-6050&dpPl=1&dpID=41-gLq5SqJL&ref=plSrch[/url][/QUOTE] You can get little clip-on heatsinks to soak up some of that heat so it's not going right into the chip.

[QUOTE=Dorkslayz;48578520]Looking for a bit of advice, I recently bought a MPU-6050 (link at bottom) and whilst I was soldering the headers on I noticed the board got quite hot - is this normal and doesn't this risk damaging the chip on the board? If so what can I do to mitigate the risk? MPU-6050: [url]www.amazon.co.uk/gp/aw/d/B00COD97LY/ref=mp_s_a_1_1?qid=1440986297&sr=8-1&pi=SY200_QL40&keywords=mpu-6050&dpPl=1&dpID=41-gLq5SqJL&ref=plSrch[/url][/QUOTE] It's fine I soldered a MPU-6050 not too long ago without any problems.

[QUOTE=Dorkslayz;48578520]Looking for a bit of advice, I recently bought a MPU-6050 (link at bottom) and whilst I was soldering the headers on I noticed the board got quite hot - is this normal and doesn't this risk damaging the chip on the board? If so what can I do to mitigate the risk? MPU-6050: [url]www.amazon.co.uk/gp/aw/d/B00COD97LY/ref=mp_s_a_1_1?qid=1440986297&sr=8-1&pi=SY200_QL40&keywords=mpu-6050&dpPl=1&dpID=41-gLq5SqJL&ref=plSrch[/url][/QUOTE] SMD components are normally designed for at least 3 reflow cycles (two board sides plus rework) because this is the most efficient way of soldering them in large numbers, so you're not likely to damage the chip by heating the board like that.

Chryseus or whoever can help me: I'm trying to find a circuit or at least an article that describes how I would build an RF amplifier for 50mhz that can give me around 30W of output. Internet resources are few and far between because most people are building 300W+ amplifiers for this frequency range and I really don't need that kind of power. I wanted to use something like [URL="https://www.rfparts.com/module/rfpower-mosfet/mosfetpowermod-vhfhp/ra30h0608m.html"]this mosfet[/URL] but they don't seem to make any designed for rf that go down to 50mhz. Hopefully you guys can help me out here. [editline]2nd September 2015[/editline] This is my only lead so far but it's in german and it requires +50V which I don't really want. (looking to run it off of 12V) [t]http://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/50MHz_35W_PA_DJ9FG.gif[/t]

What you linked to isn't only a MOSFET but includes a bandpass filter as well, any good RF amplifier will have one to reduce interferance from out of band signals and noise. That german design is pretty typical of a RF power amplifier, the high voltage would be used to minimize the physical size of the inductors since you'd need a larger gauge of wire, so it's quite possible for you to use 12V. C1, L1, R1, C2 and Dr, C3, L2, C4, L3, C5, L4, C6 are mostly the bandpass filter.

Question for you RF guys, the Pin is signal from Microcontroller or how do you get that 50Mhz signal?

Various ways, but the basic principal is that it's an AC signal in the radio frequency range. You can't get that directly from a uC without getting rid of the DC bias and even then, many uC's will have a hard time outputting a variable high-frequency signal. You could reasonably get something like 10mhz max out of a high-end ARM or FPGA, which you could then pass through a mixer + vfo combo to get you up to 50mhz.

I was about to call these the worst instructions I've ever received from a China purchase, but it totally redeemed itself. Full schematic right there, why can't everyone do that? You can almost read it even. [url=http://imgur.com/jJtg9eJ][img]http://i.imgur.com/jJtg9eJl.jpg[/img][/url]

[QUOTE=Fourier;48599839]Question for you RF guys, the Pin is signal from Microcontroller or how do you get that 50Mhz signal?[/QUOTE] To be super general about this: Almost everything is generated at audio frequencies then [url=https://en.wikipedia.org/wiki/Frequency_mixer]mixed[/url] into an oscilator (of which there can be several). But at this stage you can just use direct digital synthesis chips like the [url=https://www.silabs.com/Support%20Documents/TechnicalDocs/si550.pdf]Si550[/url] instead of multiple [url=https://en.wikipedia.org/wiki/Intermediate_frequency]Intermediate Frequency[/url] oscilators.

[QUOTE=No_Excuses;48601279]I was about to call these the worst instructions I've ever received from a China purchase, but it totally redeemed itself. Full schematic right there, why can't everyone do that? You can almost read it even. [url=http://imgur.com/jJtg9eJ][img]http://i.imgur.com/jJtg9eJl.jpg[/img][/url][/QUOTE] I got a telephone pulse to DTMF adapter in the usual brown mail packet but no instructions at all and there isn't even pin identification on the board. :v:

Heh, I upgraded my sweeper its RF plugin... [thumb]http://i.imgur.com/hGkNskR.jpg[/thumb]

After using my club's gear I have a new appreciation for any vintage HP test equipment. That stuff's incredible.

[QUOTE=papkee;48607261]After using my club's gear I have a new appreciation for any vintage HP test equipment. That stuff's incredible.[/QUOTE] Yep, HP test equipment is built to last. A lot of the 20-30 year old HP equipment we use at work is still running perfectly. Even if something goes wrong, the HP service documentation is always excellent. Almost all the test equipment in my home lab was bought broken, and I haven't had any issue with my HP gear that I haven't been able to repair.

Retro gear has the coolest service manuals. I've been looking through Roland's service manuals for the Juno-60, Juno-106, and Jupiter-8 and they literally have guides on how to fix damn near everything, schematics and pcb diagrams, and block diagrams. Its awesome! I sorta think a big block diagram poster would be neat.

[QUOTE=ddrl46;48607157]Heh, I upgraded my sweeper its RF plugin... [thumb]http://i.imgur.com/hGkNskR.jpg[/thumb][/QUOTE] So it was the tant? Next time you come across one of these awesome and cheap plugins tell me so I can fill the hole in generator with something.