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rsp

Member Since: July 23, 2007

Country: United States

Profile

Role

troublemaker

Programming Languages

all

Expertise

Creator of the Colorganic Spectralizer and Colorganic Spectralizer Kit (Sparkfun product KIT-10446).

Interests

meh

Websites

fearlessnight.com

  • It’s most likely just tracking the amount of power it takes for the IR receiver to detect the signal (by varying the LED power with the PIC DAC); the power required corresponds to the distance to the object. This is done with each LED separately and then the results are combined to calculate the X and Z positions.

  • Sure it would work; it should be interesting to see if you get better performance than a simple voltage divider and a 10 bit A/D. The eTape Wheatstone bridge configuration will give a full scale signal that’s practically linear, which is very convenient. Referring to the eTape datasheet, try using 75K for R1,R2 and 900 Ohms for Rref to get a +/-40mV signal for the HX711.

  • You are correct; this is not a true RS485 implementation. It’s more like SAE J1708, which is an OR-tied differential bus that runs at 9600 baud.

  • In Soviet Russia, Redbot programs you to follow lines.

  • Still cheaper at MCMelectronics ($41 w/shipping, plus they’re in stock, plus MCM has a bunch of nice Pi2 bundle boxes, plus spend over $100 and get free shipping with promo code GS401.

  • It’s common practice to series connect small numbers of 18650 cells without charge balancing circuitry; just be sure to use matched cells (from the same mfr lot if possible) and start them out at exactly the same voltage.

    A good match for a 7.4V 2600mAh pack of these batteries is this one, which will charge the pack in about 4 hours.

  • This is a “Decade Resistance DIY Kit”. This is not a “box” since there’s no box, knobs, etc. But looks like it could Sparkfun the bench pretty well.

    For a beginner “decade resistance box” that really is a box, try the Elenco RS-500; it has a wider resistance range, finer resistance control, and more power handling capability.

  • Nice, now how about a “Q & A” column for questions about the product? There are many questions buried in comments that have never gotten answers; this feature might clean up the comments further and make the questions easier to address. And if you want to go all Amazon about it, you could also send out emails to people that have purchased the product so they could help answer the questions too.

  • Using 3.3V logic with the panel at 5V usually works, but not always. Using no level shifting won’t hurt anything, but to work reliably level shifting is required. Unfortunately level shifting does nothing to solve the ghosting problem; that one continues to haunt me.

  • The risks of using knock-off parts is that you don’t know what you are getting, but sometimes that’s okay. Often performance and reliability is not as good as a genuine part. So knock-offs can’t be used in production, but they’re fine for hacking purposes. I would prefer to see FTDI publish a “Genuine FTDI Identification Utility” so that I can tell if I’ve got the genuine part or not. The bricking strategy is far less useful to me and does discourage the use of FTDI parts in new designs.