This seems to me to load the Arduino's output pins a lot, but I
am only using two outputs here. Be aware, you should consider
using low current LEDs with 680 ohm resistors to reduce the output
pin loading to about 7 mA per output. Although the schematic lists
330 ohm resistors, I have listed low current LEDs and higher values
for the series resistors in the Parts List to reduce loading and maybe
reduce chip heating.
You can purchase a prototyping shield for about $10 and up,
but I make my own. Simply use a piece of perfboard (0.100 inch
[ 2. 54 mm] holes center to center) the size you need, and two or
more 16-pin dual inline wire wrap sockets. As a true hacker, I save
time and shipping costs, which is important when you are on a
A nice advantage is that you can make the board as large as
you want, and add additional socket pins for headers as needed. I
just saw (cut) the wire wrap sockets in half with a hacksaw blade,
and glue the halves to the board with a very small dab of epoxy
glue between the board and socket plastic. Wait until the glue is
fully cured, then connect everything with 26-28 gauge or smaller
hookup wire to the wire wrap pins on the back side. The wire wrap
pins are long enough to give the perfboard clearance to everything
on the Ethernet shield and leave room to either wire wrap or solder
wires above the Arduino's or Ethernet shield's headers.
I did have a little bit of a problem with the SparkFun
prototyping board and had to modify it by cutting off the corner
along with a resistor and the S1 button switch to get the needed
clearance for the Ethernet connector. Using the wire wrap socket
pins, my board cleared the Ethernet connector entirely.
For the power supply, you can use the nine volt DC input jack
to the Arduino's regulator to power the Arduino, or use five and
24 volt DC wall warts connected to the driver shield terminals. I
made my own "brute force" power supply (Photo 12) by using an
IBM Proprinter transformer, having a 28.1 volt and 8. 8 volt
secondary winding as shown in Schematic 3. If you can find a
suitable transformer, the two bridge rectifiers ($0.89 ea), a 24 volt
regulator ($0.45 ea,) and a five volt regulator ($0.35 ea), along with
hacked electrolytic capacitors large enough to maintain the correct
output voltages, that is an inexpensive alternative. Heatsinks are
recommended on these regulators because they can get hot,
depending on input voltage. To transistors, heat is an enemy. Some
will question why I don't use more efficient switching power
supplies. In my case, $2.53 vs. $40 was the reason.
The code works on both the Arduino UNO and Mega 2560
model computer boards, and the Arduino and SainSmart Ethernet
shields. Both Ethernet shields have access to the same Arduino I/O
pinouts (D9 and D8), so my shields were wired to digital output
pins common to both Arduino models that did not interfere with
the Ethernet shield's communications. Note that the Ethernet shields
use digital pins D10, D4, D3, D2, D1, and D0 to communicate with
the Arduino computers.
Luckily, I have a software magician in the family — my son-in-law, Phil Hord — along with two grandsons following in his
36 January 2015
■ PHOTO 11. Close-up of SparkFun’s shield.
Modification done to clear the Ethernet
■ PHOTO 12.
A 12. 5 and 24 volt
regulated power supply.
■ PHOTO 10. Cutting wire wrap socket with