Electronics - New and Old

Heart Project

  • This is a basic digital project using a 4017, 555 timer and some LEDs. The 4017 is a decade counter that counts down one everytime it is clocked by a +5VDC (HIGH). By using a 555 timer in an Astable or occilating mode, it can clock the 4017 at a specified interval infinately. Once power is applied, the 555 will continually clock the 4017 lighting one LED at a time. Since the 4017 can only count down from 9 to 0, it was necessary to double up the LEDs on the outputs of the 4017. The top center LED is a common on the first count down. All other pairs from that point at tied together on corresponding pins. Only 9 through 1 was used, decade 0 was not used basically because it would have been one too many.

  • The picture below can better show how the LEDs were tied together.

  • Here is a shot of the wiring on the backside.

  • SMT Projects/SMT Soldering

  • I have been doing some SMT work lately, I'v been doing it by hand, ALL by hand. The PCBs are pretty easy to make. I'm using a ectchant pen and some plain copper clad board. The main trick is sizeing up everything just right, giving enough solder pad for a component and making sure traces are close enough together for everything to reach where it needs to be.

  • Below is a MAX-232 SMT chip I soldered to a hand made PCB, this was basically for practice. I was trying to teach my self the "Flood and Wick" method, not bad so far.

  • Here is my first real, workable circuit, a SMT 5VDC regulator with caps. Wasn't as hard as I thought it was going to be. The board is kinda hard to see real well because the rosin really spread out and made a mess.

  • Below is a TTL to RS-232 level converter for my Handspring PDAs. This little wonder allows for a serial device to talk to the HS units. This is a new SMT version that I am working on. The current cable I am using, I put together using the DIP version of the MAX-203 and a 7805 5VDC regulator, this is in a TO-22 case. This made for a small version, but not small enough. The new SMT version makes everything VERY small and compact. This picture shows the un-complete version. The IC and voltage regulator are in place. The two blue wire-wrap wires are for the TTL side of the chip to the HS port.

  • Do you need to check signals on your com ports?

  • I did, so I made a simple detector. I needed to check for when the RTS line was set HIGH on a 9 pin com port. I used a 2907 transistor to do the switching. You can see the base is on the RTS line (Pin 7) and the collector is on Pin 5. The emmiter is soldered to the anode of the LED and cathode is soldered to ground (metal case of the connector). This could be done for every pin, in fact I plan to build a more complete version for the TX, RX, RTS, CTS, DSR and DCD lines.

  • Here is my workbench, probaly not the best way to go, but I still crank out project after project :o) You can see my collection of "semi-retired" mobiles that have been transfered from the truck and put into service at the bench. Plus, if you look closely at the bottom left of the bench, you'll see some finished PIC projects on perf-board. All of the little white cards are backings from RadioShack parts.