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dmg

Thu Feb 18 2010, 04:08AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

I wondered what small mini projects everyone was doing.
If you wish to, feel free to share.

here is mine:
its a TC controller, with solid state relays on one of the power inputs (still not sure whether for a motor, or the DC supply)
and a PLC to regulate other non-important subsystems, (fans, lights etc..)
some SCR switches here and there, a 12 to 24 converter, a test light, and other junk

it is still not finished, needs more parts, and a plexiglass interface with some fans and switches mounted on it. I need to feed cables through the box, under the black/grey foam outside of the wood, there is a good deal of aluminum tape, to funtion as a poor mans faraday cage (not that I will need it, but just incase.)

and I will probably modified the ladder logic of the PLC for some more funtions (I have 20 Y + X spare terminals and 3 reserve terminals LOL) - incase anyone wonders, its an mitsubishi FX-48MR-UA1 (FX2n family) and I got it for free.

like the mythbusters say: if it's worth doing, its worth over doing.

EDIT: your projects do not need to be completed, or even for that matter, started, posting plans for said project is perfectly acceptable.

Hazmatt_(The Underdog)

Thu Feb 18 2010, 06:25AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Nice of you to ask,

I've been working on some power amps for a looonnnggg time now.

The pictures are of the multi-winding iso/non iso phase splitter
5W broadband driver amp with 2 phases 4 out for driving high power amps
12W 10KHz to 1.1MHz amp
was the 100W test bed, but is barren now
180W amplifier, was playing with it and pushed it too hard sorta on purpose, awaiting rebuild and full biasing
5KHz to 10MHz dBm power meter to 1KW

When all is done, I hope to have a 200W and 400W 10KHz to 500KHz broadband amp with dBm meter! and gain leveling, just like the big boys.

Steve Conner

Thu Feb 18 2010, 10:57AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

A Douglas Self "Blameless" hi-fi amp!

I tested the short circuit protection successfully last night, and will post the results of that in the next few days.

This is a functional prototype only, hopefully the finished amp won't look like that

I plan to mount a stereo pair of them in a nice finned aluminium case that I salvaged from an old power supply.

Dalus

Thu Feb 18 2010, 10:11PM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

Been playing with field sequential 3D for a while driven by the urge to be able to see avatar in 3D at home. Bought some shutter glasses and designed a driver circuit for it. It works but I still need to document it. But somehow I don't feel like doing that right now (hint been documenting a uni project 3 times for just one project).

4363874916 354f9149eb

[Edit: Oversized picture garble bllurgh glbub blub]

The project at the university was quite fun we had to identify and sort 4 train carts on a model train track. We had to design our own hardware and software to run on an xilinx fpga. The main problem was that they designed this project to give a lot of EMI so that had to be dealt with.

Here are some youtube clips. Btw we managed to break the speed record on the official run

we fixed the part where we had to intervene so the trains didn't collide.

Sulaiman

Thu Feb 18 2010, 11:49PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Steve, your amp can't be blameless - you haven't used teflon coated litz stranded silver plated oxygen free copper wire - what are you thinking !
(I'll hardly mention not using audiophile grade capacitors)

Two thoughts;
1 - which costs more (money/time); the amp or the equipment to measure it?
2 - have you considered 'active' speakers?
2.1 I can vouch for the sound benefits of separate amps for each driver bandwidth with active crossovers before the amps.
2.2 I had a quick 'play' with positive feedback of driver current to the input to compensate for the driver resistance - a negative output resistance amplifier with loop gain set below oscillation. You may find it interresting.

Briefly, out of curiosity,what is the open-loop bode plot like?
I lost interrest in hi-Fi when my hearing became Lo-Fi

Steve Conner

Fri Feb 19 2010, 07:56AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Great projects all :)

Sulaiman: The equipment cost considerably more than the amp, but if I costed my time building it, that would be more expensive still! It's a learning experience though, I always wanted to make one, and I haven't done any "real" discrete electronics in ages.

I know active speakers are better, but I already have a few pairs of good passive ones, and they go as loud as I (and my neighbours) can stand without the amp clipping.

Negative resistance is fun, but commercial speakers are designed to give a flat frequency response with zero resistance drive. Negative resistance would upset them as much as excessive positive resistance, like you get from an old valve amp.

The bode plot is hard to measure, but from theory I can tell you that it's like an ordinary op-amp. So the feedback is huge at low frequencies, maybe over 80dB, then it falls at 6dB/octave until it gets to about 30dB at 20kHz. 20kHz is where you set the loop gain, the low-frequency pole hardly matters, but the lower it is, the better the ripple rejection will be.

I remember when I used to be able to hear 21kHz too! Down to 15 now :(

Oh and the short circuit protection worked! I plotted out the results, drew some load lines on there, and it suggests that if I add another pair of transistors, I can run +/-40V rails and just about drive a 4 ohm reactive load. I'll probably use +/-35 because I have a transformer for that voltage.

uzzors2k

Fri Feb 19 2010, 10:45AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

I'm working a TV tuner radio scanner as a sort of mini project, and an underwater ROV as my "main" project. I've purchased some 10W leds, CMOS camera, composite to USB adapter and other goodies, but I haven't done much actual work on it yet. Planned maximum depth is 30 meters, which should reveal some neat things I can't see while free diving. I desperately wanted to have a depth sensor on it, but the only cheap pressure sensors I can find are the atmospheric types, unsuitable for use in water, let alone sea water. Control will be over cat5 cable, with inboard batteries.

Dennis Rogers

Sat Feb 20 2010, 02:17AM

Registered Member #1837 Joined: Tue Dec 02 2008, 02:20PM
Location: NYC
Posts: 65

Uzzors wrote ...

I'm working a TV tuner radio scanner as a sort of mini project, and an underwater ROV as my "main" project. I've purchased some 10W leds, CMOS camera, composite to USB adapter and other goodies, but I haven't done much actual work on it yet. Planned maximum depth is 30 meters, which should reveal some neat things I can't see while free diving. I desperately wanted to have a depth sensor on it, but the only cheap pressure sensors I can find are the atmospheric types, unsuitable for use in water, let alone sea water. Control will be over cat5 cable, with inboard batteries.

Cool project. One thing to think about is the Cat 5 cable. Any solid wire cat5 (which is most) will fail after a certain number of "flexes". You need stranded wire to be able to flex reliably, as in a traveling cable for a ROV. Of course cat5 is dirt cheap, so if it is not to be used too much and a failure wont ruin your day, it still may be the best way to go. Try and get stranded if it's not too much more money though.

Turkey9

Sat Feb 20 2010, 07:20AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

I'm working on a modified version of the PIT (pulsed inductive thruster). It will be smaller but should provide just as much if not more thrust. Loving getting my vacuum chamber up and going. All the pumps and plumbing is together but I just burnt out a used ionization gauge tube so I can't measure it... I get to use all the fancy Teflon coated wire and vacuum safe components!

klugesmith

Sat Feb 20 2010, 08:07PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Aside from activities like those of my family, neighbors, and co-workers,
the backlog is too long to list. Things worked on this month:
1. Vacuum hardware for a science workshop program.
2. X-ray detection and measurement
3. Rogowski coil analysis & measurement
4. Drying out molding sand for old backyard foundry (Found molding mud after rainstorm)
5. Finishing the greenhouse (Roof vent design is incomplete - need to figure out glazing).
6. Getting a safe shot at any of the marauding squirrels

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