ANDREW’S $100 ELECTRONIC WORKBENCH CHALLENGE ENTRY
Early in the process of selecting items, I decided to base my The carrying case is a bonus.
purchasing decisions toward the goal of stocking an entry-level A desoldering tool and alligator clips complete the tool
robotics and industrial automation workbench. Over the course of package for entry level usage. While we can strive to never make
recent years, hobby-bench level electronics have been focusing on a soldering mistake, inevitably it creeps in, regardless of skill
the usage and programming of microcontrollers. These devices level, and the desoldering tool can save the day. Alligator
have allowed for the increasing simplification in designs that clips provide quick hookup of parts that just need temporary
would have taken many more discrete components in the past to connections during prototyping.
implement. Instead, the complexity of hardware is reduced by
implementing more functionality in software.
I felt that stocking a general-purpose workbench went against
this reality, and so the decision was made to focus my selections
around the standard, widely-used PIC16F84A microcontroller.
Narrowing the focus even further to robotics applications adds an
element of excitement — the student’s projects can now move,
and the results of their development can be seen in a tangible way.
I decided to focus first on the tools. I wanted them to be
quality tools that the student could use potentially for a lifetime,
provided they are well taken care of. At the same time, I had to be
mindful of cost. This necessitated the goal of obtaining as much
functionality as I could for the price from each tool in the set I
A good multimeter was a must. While certainly not a Fluke, I
personally own a couple of the low-cost multimeters I selected
for this workbench, and I have found them to be very capable
and reliable tools for a fraction of the cost. The good selection
of ranges, transistor/diode testing capabilities, and small size
make this multimeter an excellent introductory choice for the
workbench. The soldering iron seemed like a good selection
because it is of a low enough wattage to handle some of the
more fragile components without overheating, while still having
enough power to solder larger components with ease. The grip
seemed like it would be comfortable for longer periods of use,
and the grounded plug should help with ESD issues.
The soldering iron stand combines both a third-hand with
magnifier with a soldering stand complete with sponge, which
means less room on the workbench taken up by individual tools
(which is always a plus when prototyping and assembling
circuits). The magnifier allows for easy visual inspection and
correction of solder joints as needed. A small but adequate
amount of 60/40 solder rounds out the soldering station supplies.
The 25 piece Velleman tool set is similar to a tool set I own.
For the price, it cannot be beat on the necessary selection of
tools you get: miniature wire cutters, long nose pliers, tweezers,
multi-bit screwdriver, and a selection of precision screwdrivers
are all included. All are very handy to have on the workbench.
All electronic workbenches need prototyping tools. The
solderless breadboard chosen affords the student plenty of room
to develop and test a variety of microcontroller interfacing
circuits. Hookup wire can be used for soldered connections or as
wire jumpers on the solderless breadboard, at a price point much
lower than formed wire jumpers. A battery holder and connectors with four AA batteries provides a simple and portable DC
power source for development. Finally, the prototyping PCB —
with parts — can be assembled as a carrier board for the
microcontroller, which can then be easily interfaced to circuitry
developed on the solderless breadboard.
As mentioned previously, the standard, easy-to-use
PIC16F84A was selected as the microcontroller for this workbench. A 20 MHz part was chosen to allow for future upgrades in
speed, if so desired. The prototyping PCB discussed above was
designed to use a 4 MHz oscillator crystal/resonator. The PIC
selected can run at this lower speed, being rated for DC- 20 MHz
operation. To allow the user to program the PIC, a programmer
is necessary. The following design was selected due to the
simplicity of its construction, and the need for only standard and
simple parts. Power for programming is derived from the host
PC’s serial port. Parts for the programmer are included in the list,
while leaving enough parts for the student to prototype and
construct other circuitry on the solderless breadboard, or
elsewhere. The PIC16F84A is plugged into a socket on the
programmer. The assembled hex file is uploaded to it, then the
PIC is moved to the carrier board and interfaced to controlled
circuitry as desired. The development software for creating the
hex files can easily be found as open source software for most
platforms, and is thus free for use by the student.
Various other passive and active components are provided
to allow the student the capability to construct a variety of
control and automation circuits. LED flashers and sequencers,
relay and H-bridge motor control of a small DC motor, control
of RC servos, and input from buttons and leaf switches are all
capable of being constructed using the components provided,
allowing the student to develop a wide set of skills and
knowledge of robotics and industrial automation.
Projects utilizing these parts can be easily found on
the Internet by the student. There is a plethora of designs
and code available for the PIC16F84A; it is easily one of
the most utilized microcontrollers in existence, mainly
due to its simplicity and low cost.
Qty Item Vendor Part # Price/ea
1 Multimeter jaycar.com QM1500 $4
1 Soldering Iron circuitspecialists.com 200PHG-25WATT $6.95
1 Soldering Stand goldmine-elec-products.com G12810 $4.98
1 Solder allelectronics.com TS-110 $1.25
1 Toolset designnotes.com VTTS $9.85
1 Desoldering Pump electronics123.com VTD1 $2.91
1 Alligator Leads circuitspecialists.com M000F0003 $2.49
1 Hookup Wire
1 Battery Holder 4AA
1 Battery Clip 9V
1 Batteries 4AA
1 Prototyping PCB
I was unable to include everything I wanted to in this
workbench (in particular, I wanted to add a simple
oscilloscope or at least a logic probe, but neither were in
the cards). By careful selection and research, I believe I
have managed to include the necessities needed for the
introductory student to explore a large swath of territory
within the fields of robotics and industrial automation.
This contest proved quite an eye-opener for me. I
had thought it was going to be simple; a virtual walk in
the park. Instead, I found myself neck deep quite quickly,
making decisions on parts and vendors based on costs,
quantities available, and quality. I ended up with a new
respect for individuals who have to do this on a regular
basis — for their job, their students, or otherwise. Total
cost for the entry $99.36 with $0.64 left over for some
bubblegum (well, maybe not at today’s prices!).
September 2008 81