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oneTesla - a small single-board DRSSTC

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Steve Conner

Sat Dec 29 2012, 11:10AM

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

I think having OCD might make for a better user experience if you plan to sell a lot of the things to complete noobs through Kickstarter. Of course they can still blow it up by building the OCD circuit wrong.

mikeselectricstuff

Sat Dec 29 2012, 08:47PM

Registered Member #311 Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253

A few random comments (aside from the obvious safety & liability issues that could arise from selling a TC kit to the kickstarter demographic...)
The interruptor doesn't seem to have a power LED - for a battery powered unit an obvious ON indication would seem rather useful. Ditto an indication of MIDI data.
Lack of a manual pitch control and fire button to allow MIDI-less operation seems somewhat bit penny-pinching.
Running the AVR at 16MHz, and using a 7805 regulator is probably at least doubling your standby power draw from what it could be.

As there's no full schematic (yet?) in the guide, the power arrangements appear unclear - why is there a DC jack on the main unit ? Is the LV section powered seperately? if so I wonder how wise this is, as the DC power lead will be rather vulnerable to noise pickup and strikes.

If seperately powered, it appears that there is no visible indication of primary circuit power being on. If this is really the case I think this is a rather serious safety omission.

No mains filtering.. at all....?

$209 seems rather a low price to cover costs of parts, kitting, packaging and all the other hidden work - I doubt you'd have got many fewer takers at $249

Dr. ISOTOP

Sat Dec 29 2012, 09:34PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Thanks for the advice, Mike

The interrupter will have a LED's on it next time, I forgot to add them when sending out this revision. Ditto on the mains power indicator.
The LV section runs off a 19V adapter. Haven't had troubles with noise pickup so far.
I might add a mains filtering choke if I can make room on the board; sadly, the main source of trouble is going to be the fact that the secondary is grounded to mains ground, and there's not much I can do about that (hence why the manual says to float your laptop and unplug nearby electronics).

mikeselectricstuff

Sat Dec 29 2012, 11:52PM

Registered Member #311 Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253

Another useful addition might be an audio input with preamp, e.g. for guitars etc.

Jazzman56

Mon Dec 31 2012, 01:44AM

Registered Member #7222 Joined: Sat Oct 13 2012, 06:04AM
Location:
Posts: 18

Dammit was checking this thread almost everyday and i missed the launch and the $209 early version :(

Ohh well better get saving :P

Thanks for releasing the KIT

Steve Conner

Mon Dec 31 2012, 12:05PM

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

Mike, if you were worried about noise issues with the DC input cord, you should probably be even more worried about a high-impedance, low-level analog audio input.

mikeselectricstuff

Mon Dec 31 2012, 02:22PM

Registered Member #311 Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253

Steve Conner wrote ...

Mike, if you were worried about noise issues with the DC input cord, you should probably be even more worried about a high-impedance, low-level analog audio input.

Yes but the former is at the base of the coil, the latter is on the other end of a length of fibre so can be put far enough away.

Steve Conner

Mon Dec 31 2012, 04:02PM

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

Good point, when I started writing that post, I didn't even notice that the system used a fibre optic link. It was advertised as a single-board system, so I assumed they put the interrupter on the same board as the power circuitry.

HV Enthusiast

Sun Jan 06 2013, 05:05PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Responded to your PM - PM Sent.

E.TexasTesla

Mon Jan 07 2013, 01:57AM

Registered Member #4362 Joined: Sat Jan 21 2012, 03:44AM
Location: Texas
Posts: 98

Hello, Im having a problem with the midi interrupter board.
Software "Polyphonic MIDI-based DRSSTC interrupter (Version 1.0)"on an atmega328p.

What should the signal look like going into pin two of the arduino? Its currently at 5v and drops down to 4.5 volts during keystroke. I dont think thats enough change for valid serial input to atmega.

Im using a yamaha psr-170 keyboard with midi out.
When I power up the interrupter board and play a note I get no output from the fiber optic transmitter.
I've checked for 5v from pot. indicating its set to max.My signal to pin 2 at arduino is nice and square.

I figured my midi signal was weak so I bypassed the 220 ohm resistor between midi input and 4n25.
This dropped the signal down to 4 volts during key stroke but still no output from arduino.

I figure my keyboard is old and the midi signal may not be compatable with the software.
By the way congats on the kickstart program. Looks good.

EDIT: I replaced the 4n25 with another one and now my signal swings from 5 volts to 3 during keystrokes.

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