Welcome to the MIDI Sprout forum

Author Topic: DIY  (Read 2797 times)

Offline alka

  • Newbie
  • *
  • Posts: 11
  • multi-faceted like crystal.
    • View Profile
    • alka and the hexagram
DIY
« on: May 16, 2016, 01:38:16 PM »
Firstly, thank you for sharing the files for the sprout. Looking to build one or two for personal artistic use and for interactive use in my library's community garden. Perhaps I am overlooking the information but what voltage value LEDs are you using? As I would be creating a soldered version, what resistor values would you recommend before the LEDs?

Offline alka

  • Newbie
  • *
  • Posts: 11
  • multi-faceted like crystal.
    • View Profile
    • alka and the hexagram
Re: DIY
« Reply #1 on: May 16, 2016, 02:06:23 PM »
Is it safe to assume 3V LEDs, 4.5V DC, 25mA, therefore 68 Ohm resistors?

Offline alka

  • Newbie
  • *
  • Posts: 11
  • multi-faceted like crystal.
    • View Profile
    • alka and the hexagram
Re: DIY
« Reply #2 on: May 16, 2016, 04:03:31 PM »
I just found in the schematic diagram notes where 220Ohm resistors are recommended for the LEDs... 6 resistors with 220Ohm resistance on 3V LEDs meaning only 7mA of current or am I misunderstanding something?

Offline sam

  • Sam
  • Moderator
  • Full Member
  • *****
  • Posts: 187
  • Understand How Your Tools Work!
    • View Profile
    • Electricity for Progress
Re: DIY
« Reply #3 on: May 16, 2016, 09:05:01 PM »
Hey Brian! To be honest, I went through a few different LEDs in the design and ended with 220 ohm as
 I got a great deal on a pile of 220s. We get better diffusion, at the cost of burning some current.


Offline alka

  • Newbie
  • *
  • Posts: 11
  • multi-faceted like crystal.
    • View Profile
    • alka and the hexagram
Re: DIY
« Reply #4 on: May 17, 2016, 11:50:15 AM »
Great Sam, thanks! Looking forward to diving in. I'll be experimenting with your direct CV out as well. My current primary modular however ranges 0-10V and whereas I'm sure I'll be able to effectively experiment with the 5V output of the MIDI Sprout I may look into adding on a voltage booster. What are your thoughts on something like this: http://www.arduino.cc/playground/Main/RegulatedPositiveVoltageBooster ?


Offline sam

  • Sam
  • Moderator
  • Full Member
  • *****
  • Posts: 187
  • Understand How Your Tools Work!
    • View Profile
    • Electricity for Progress
Re: DIY
« Reply #5 on: May 17, 2016, 01:50:18 PM »
If you need to boost the voltage from the built in CV 0-5(ish)V of the Sprout up to a higher level, I suggest using a vactrol (LED and Light dependent resistor) as a variable resistor in a simple voltage divider.  This will let you safely control voltages up to your modular's rails.  Also could try using a transistor (MOSFET) to boost and control the voltage.

Of course, if you need 0-1v for your specific application, an 'attenuverter' (TL084) will cool down that voltage or even swap its polarity.

The amazing peter edwards has some advice on his Casper Electronics site.
« Last Edit: May 17, 2016, 01:54:33 PM by sam »

Offline alka

  • Newbie
  • *
  • Posts: 11
  • multi-faceted like crystal.
    • View Profile
    • alka and the hexagram
Re: DIY
« Reply #6 on: May 17, 2016, 02:05:56 PM »
Ah, perfect advice. I will look into the vactrol solution.. makes sense as I'm looking to interface with a Buchla machine and have plenty laying around from some recent builds anyhow!

Offline alka

  • Newbie
  • *
  • Posts: 11
  • multi-faceted like crystal.
    • View Profile
    • alka and the hexagram
Re: DIY
« Reply #7 on: May 20, 2016, 11:43:22 AM »
just remembered I had one of these laying around... any advice for effective hookup? Would this do the trick to boost (knowing that's a bit overkill)?

https://www.pololu.com/product/2571

Offline sam

  • Sam
  • Moderator
  • Full Member
  • *****
  • Posts: 187
  • Understand How Your Tools Work!
    • View Profile
    • Electricity for Progress
Re: DIY
« Reply #8 on: May 22, 2016, 11:31:00 AM »
It depends on how you would arrange the booster.  If you used the booster to provide a higher rail and then used a vactrol or other method to follow the voltage.  But i think the booster would drain the batteries on the Sprout very quickly.

Offline alka

  • Newbie
  • *
  • Posts: 11
  • multi-faceted like crystal.
    • View Profile
    • alka and the hexagram
Re: DIY
« Reply #9 on: May 31, 2016, 11:07:18 AM »
Soo.... if I were to add a 5VDC adapter plug (which switches off the batteries when plugged in), would you recommend any additional capacitors for decoupling?

Offline sam

  • Sam
  • Moderator
  • Full Member
  • *****
  • Posts: 187
  • Understand How Your Tools Work!
    • View Profile
    • Electricity for Progress
Re: DIY
« Reply #10 on: June 02, 2016, 11:28:28 PM »
If adding a direct 5V from a USB or other regulator, the short answer is no it will work fine, the long answer is ... heck yeah you should decouple that at the source and at each IC.

When i have used the Sprouts for long term installations (1 month+), I just hacked a usb phone charger with some alligator clips.