» MAKE: NOISE — Discuss this article

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• errors in schematic
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  In schematic: bass_step_2a.jpg
  
  The resistors for the LEDs are 1000x too large. They should be 440 Ohms instead of 440K Ohms.
  
  The bill of materials from the original articles says 440 Ohms.

  Posted by Aras on March 28, 2009 at 20:24:26 Pacific Time

• missing component values.
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  I really dislike these types of schematic drawings. There's really no benefit to having mspaint-style bolded graphics.
  
  Anyway, someone who knows about op-amps can figure this out, but someone who doesn't might feel frustrated trying to determine missing resistor values.
  
  Also, the resistor value going to the "ON" LED should probably be increased from 440 (already correcting for the "k" misprint) to about 1.5k (1500 ohms). This will reduce the brightness, but also reduce the load on the battery supplying +9V. No need to drain this battery faster than necessary.

  Posted by samurai1200 on May 04, 2009 at 09:40:27 Pacific Time

• missing component values.
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  The materials list includes two 100K-ohm resistors per string, and
  yes, the schematic should have the two resistors labeled 100k. The materials list includes 440k resistors, and as the blog post suggests this should read 440ohm. Also, the 440 ohm resistor is a compromise. As the comment says, a
  larger resistor will help prevent battery drain - but I also wanted users to be able to add multiple IR transmitter LED's in series without having to change that resistor value. So the value of 440 was chosen as a compromise - the indicator LED will work fine with a 1k resistor as well.
  -len

  Posted by Lenkeeler on May 04, 2009 at 15:01:49 Pacific Time

• twang me
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  has anyone built this circuit lately? does it work? i see several parts on schematic have been corrected:
  10K resistor btw. capacitor & pot is now 100K, pot is 1M. how about 1K resistor @ photodiode emitter & 10K at op-amp -- same? author notes "2 110K resistors per string" -- where is 2nd one?
  

  Posted by chris losee on October 21, 2011 at 15:02:26 Pacific Time

• twang me
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  that should have said "two 100K resistors per string"

  Posted by chris losee on October 21, 2011 at 15:04:10 Pacific Time