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121  Using Arduino / Sensors / Re: Is there anything called vibration censor? on: August 26, 2012, 06:39:23 am
Another possibility would be to use a piezo element in some sort of padded pouch so it doesn't get punched to death  smiley-twist Have one in the target area, and sample the signal from it with an op-amp circuit and the ADC of an arduino or whatever mcu board you happen to be using.

Then, have something in your program that will map that data to one of several discrete options, from featherweight to Hulk Smash, and output THAT data over your serial port to the computer. That's how I'd approach the problem anyway, it may not necessarily be the best but it makes sense in my head.
122  Using Arduino / General Electronics / Re: How much WATTS do I need? on: August 26, 2012, 06:33:25 am
The LM386N is a good choice here. I messed about with them a bit, some years ago... easy to use, difficult to fry (as long as you don't deliberately abuse them). Google image search threw up about a million schematics to try, none of them are hard to build.
123  Using Arduino / Installation & Troubleshooting / Re: Output Voltages differ for different power supplies to the arduino. on: August 26, 2012, 06:24:42 am
If I remember right there's a bit of wiggle-room in what devices consider a logic high/low. I don't think it HAS to be bang-on 5.0V, just above a certain threshold. I power my stuff using LDO 5V regulators and usually, unless it wants a lot of current, a PP3 battery (because I have hundreds of the bloody things), and it always ends up pretty close to the 5V mark smiley
124  Using Arduino / Project Guidance / Re: Outputting a voltage on: August 23, 2012, 11:18:01 am
Yes, but not directly. You'll either need to use a PWM output and run that through a low-pass filter to get your voltage, or use something like a SPI/I2C interfaced DAC to do the job. Depending how much precision you want, I might be tempted to start with the first option as you only need a resistor and a capacitor smiley
125  Using Arduino / Project Guidance / Re: time counter on: August 19, 2012, 07:31:29 am
Even though the value stored in millis() rolls over after a certain length of time, you're only checking to see if it's increased by 1000... so it doesn't matter! It's not as if your code will drop dead as soon as it rolls over, it'll just start ticking over from 0 again and your other variables will stay how they were.

To print more than one number, just repeat that statement! The 7219 will latch it's digits so they won't change until you write something else to that location. I did have some example code somewhere, but I can't find it smiley-sad Sorry.
126  Using Arduino / General Electronics / Re: Is this the circuit I need, or something else? (Envelope generators) on: August 17, 2012, 04:15:31 pm
Ahh slight trail-of-thought fail in my original post smiley The outputs from that circuit are supposed to feed into the CV input of one of the various voltage-controlled amplifier circuits I have coaxed out of Google - I haven't decided which one to build yet but the simplest one seems like a good place to start!

Perhaps something like this: might be a good starting point to experiment with?

The one thing I can't figure out just by looking at the envelope generator schematic is whether or not the attack level will ALWAYS eventually go up to the maximum, or does it's max level depend on the peak voltage of the trigger pulse? Might be one of those "build it and see" things... if the output level is proportional to the input (e.g. for a very basic sort of velocity sensing on a trigger pad), then I'm in business. If not, then I'm stuffed and need something else.


127  Using Arduino / General Electronics / Is this the circuit I need, or something else? (Envelope generators) on: August 17, 2012, 01:18:27 pm
Here's what I'm looking at right now:

What I want to achieve is individual Attack/Release controls for several channels of a drum synth (which, for many reasons including the fact I'm still a shitty coder, is leaning more towards being analog in nature), and also to provide a pitch EG where required. In my mind's eye I pictured having a board built up to host all the EG circuits, with the various gate outputs collected together on a header to go off to all the VCA/VCO control inputs.

This looks reasonably simple and buildable, and although I don't have any TLO74s I do have plenty of TLO81s which look like they might be a suitable substitute. Should I be looking at something else or is this circuit worth building and experimenting with?

128  Using Arduino / Programming Questions / Re: Parallax laser range finder need help on: August 13, 2012, 02:53:02 pm
Sorry for not actually posting a reply offering help, but would you mind telling me which LRF you have? I wouldn't mind getting one myself and having a play-around.
129  Using Arduino / Audio / Getting a wav file onto an EEPROM (or into flash memory) on: July 30, 2012, 12:53:29 pm
I've been doing a bit of research/work on the drum machine project idea I had a while back, and I'm trying to wrap my head around how best to process a wav file in order to dump it either into flash memory or, as is more likely, onto an old-style parallel E(E)PROM. I don't have a programmer yet for said ROMs but I can go shopping for one next payday - in the interim I want to test the files from the flash memory of one of the ATmega328's I have knocking around. A single sample is about 18.7kb, so one will fit smiley

The general idea for a rough-as-guts test bed is to simply shove all the data out in parallel on PORTD or something, through a DAC and see what I get (if anything) on the other end. I'd rather have some idea if it's going to work before going equipment shopping!

So far, I have:

Wave files processed in Audacity and exported as RAW(header-less), unsigned 8-bit, 32khz mono.
A HEX editor, specifically Frhed, which I have so far used for comparing the "normal" wav with the header-less one just for a look, and exporting the data as a hexdump text file.

What's the best way to get the compiler to take this data and shove it in flash memory as a great big array so I can read through it from my main program? I'm googling in another tab as I write this, but it's a bit hit-or-miss not knowing exactly the technical programming terms for some things.

130  Using Arduino / General Electronics / Re: Does the color of the laser make any difference? on: July 28, 2012, 07:30:42 am
I would not advise wearing a red shirt while working with lasers - I've seen enough star trek to know how that works out. smiley-wink

Seriously though, I think there's a bit of irrational fear about lasers on many forums. Same as HV projects. IF you are aware of the risks, and IF you wear the right protective gear and use your common sense, then there's no reason not to have a go.

I have no need to play with lasers (yet) as I haven't thought of a project I want to work on that requires them. But if I was going to, I would definitely make sure I had some protective goggles intended for the laser wavelength I was working with, and I would probably run any experiments remotely and observe the results indirectly, perhaps from outside the room on a monitor. I would think with those safety measures in place even an amateur would have a hard time causing themselves serious injury.
131  Using Arduino / General Electronics / Re: Buying New Soldering Iron [High End] on: July 25, 2012, 11:11:07 am
I need to upgrade as well... I have my eye on a Weller WD-1M with a WP120 iron, but in the likely event I can't afford it, I'm willing to settle for an Antex 690SD smiley
132  Using Arduino / Microcontrollers / Re: Building a dual core Arduino with two ATmega328 on: July 24, 2012, 01:47:59 pm
Some of the more complicated projects I have in mind would benefit enormously from having a dual-MCU setup. I think it's a perfectly reasonable way of handling complex tasks if, like me, you lack the necessary coding skills to pull it off with a single high-end chip and aren't all that bothered about minimizing hardware costs for mass production smiley One such idea was for an 80s style drum synth, and while the current "solution" is to use one MCU for all input control scanning and display twiddling and a whole other one for sample playback, I am sure a decent programmer could do the whole thing on a single processor.

I suppose it depends what you're better at. If you're more comfortable with complex hardware than tricky code, then two Arduinos (or equivalent) might be a good way of approaching a problem.
133  Using Arduino / General Electronics / Re: Constructing a high-voltage transformer for safety and ruggedness on: July 17, 2012, 02:05:47 pm
When putting together your prototype driver circuit, include the ability to vary the pulse frequency.  These transformer cores have a natural frequency that will allow the most efficient/effective operation.  You can even vary output voltage by keeping voltage constant, but simply changing the pulse frequency.

Ahh yes, good advice smiley Should I build the oscillator stage so that both freq. and duty cycle can be tweaked, or is there no real benefit in altering the duty cycle? It seems like building the capability into the first prototype might be an idea, just to mess around and see what it does.
134  Using Arduino / General Electronics / Re: Constructing a high-voltage transformer for safety and ruggedness on: July 17, 2012, 01:31:09 pm
Because I only have the cores, that's why smiley-wink True, I COULD scrounge up complete transformers... but I was more thinking about the best way to get what I want with the scraps, bits and bobs that I already have. Aside from suitable terminals I pretty much have all the stuff I think I need. Besides, on the whole I thought it might make for a much more interesting and rewarding build, as long as there's no glaringly obvious safety issues I've overlooked.

I've got a sort of miniature version of the driver circuit built up, it's working with a camera flash transformer at the moment - somewhat under-spec for charging up large cap banks, and I doubt it's very efficient  smiley-razz But it DOES work... I can get about 760V post-diode out of it at the moment without magic smoke/bad accidents.
135  Using Arduino / General Electronics / Constructing a high-voltage transformer for safety and ruggedness on: July 17, 2012, 10:48:13 am
I have some ferrite cores from old flyback transformers which I'd like to use to wind my own coils around. I have an idea of how I want to put things together to make sure it's safe from arcing to anything (including me), and I'd be interested in any feedback on my design plans. No pics unfortunately so try and visualise if you can:

The coils themselves will be wrapped around PVC conduit. It seems to be a good diameter for the job and I have plenty of offcuts knocking around. Between each layer of the secondary I will use PTFE tape.

The windings will be resting on some plastic stand-offs inside an ABS project case. Each end of the windings will be brought out to a suitable terminal (which I have yet to choose) that I can screw into from outside the box. Once I'm happy with the electrical characteristics of the thing, I intend to fill the WHOLE thing with epoxy potting compound, so each and every part of the transformer is covered and surrounded.

I'm hoping to achieve an output of around 1kV, for various cap-charging activities and possibly other experiments. Other safety considerations are PPE (I have gloves good to 1kV, so they say on them) and I'm pretty sure somewhere I have an air-pressure switch which would make a suitable remote control.

What have I overlooked? Does this seem like a good way of going about things?

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