Ultrasonic Distance - discrete components

Discussion in 'The Projects Forum' started by GopherT, Oct 29, 2015.

  1. GopherT

    Thread Starter AAC Fanatic!

    Nov 23, 2012
    Here, since I am too lazy to put everything together for a 'completed projects' thread, I'll just post it here for your viewing pleasure.

    Measures distance in inches to the nearest 0.1" or centimeters (switch).

    All discrete components 4000 series logic. No micro-controllers! My first reasonable size project all "retro".

    Something fun to do with a $2 ultrasonic sensor from China eBay. The Ping))) sensors from Parallax seem to be better built but are more difficult to deal with because it is a three-pin device (same pin is input to trigger and becomes an output for the pulse.

    Sorry about picture quality - gen2 iPad.


    Sinus23, strantor, atferrari and 2 others like this.
  2. atferrari

    AAC Fanatic!

    Jan 6, 2004
    Could you post a schematic and a minimal explanation G?
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    Nice layout technique, kept it single sided without many jumpers. The power routing is a bit old-and-out-of-favor school. I don't see mounting points for the 78xx heatsink. What is the system power?

  4. GopherT

    Thread Starter AAC Fanatic!

    Nov 23, 2012
    Everything was made from junk I had acquired over the past 7 years of this hobby. Some worked as planned, some did not. Therefore, the heat sink was a last minute addition and no mounting holes on this iteration. I planned to use a smaller heat sink to go with a 7.5VDC walwart I had from an old (20-year-old) baby monitor. After designing everything, the barrel connector did not match what I had as a connector and the cord was brittle so I went for a 12VDC walwart (only one I had with matching barrel connector). Also, the Ultrasonic sensor was supposed to draw only 250 mA when activated and "low current" on standby. Unfortunately, that is not quite true. It draws about 150mA on standby. Finally, the LEDs were not as bright as hoped for at 4.4 mA so I goosed them to 12mA on the display.

    So, instead of 125 mA draw (all segments on), I am up to 400 mA . Instead of dropping 2.5V from a 7.5V supply, the poor little 7805 is dropping 2.8 Watts! (depending on the number of display segments lit). Needless to say, I don't let this one run long until I get a different walwart.

    In the next iteration, I will buy a microUSB connector so I can just use a cell phone charger. Or, I will just hardwire the cell phone charger to the PCB - I don't know how small the wires are there, let me know if you have had a bad experience trying this before I ruin one of my chargers.

    Interestingly, I have two sets of those 1" tall LEDs, one is CC and one is CA (Same mfg, and same model). The CA is much, much brighter at 5mA than the CC at 12 mA per segment. Anyhow, the evolution continues. I have several people asking for one so I will continue to evolve it.