counted and saved in the nonvolatile EEPROM on the
microcontroller. Knowing the IR period allows us to
accurately count this number of IR carrier pulses. Noise or
a different carrier frequency is rejected because the carrier
frequency and therefore the period would be incorrect.
Once ‘trained’ and in operation, the same logic is
reapplied with each received IR signal. The incoming
carrier period is compared and the incoming pulse
sequence is compared to that which is saved in the
microcontroller’s EEPROM. If there is a match, the
microcontroller sends an SPI format signal to the digital
potentiometer IC to bump up, down, or turn on or off the
After each volume change or toggling the mute, the
current volume setting is saved in EEPROM so that the
volume setting will be the same when coming up from a
loss of power.
I’ve included (at the article link) the files needed to
build a very small (I wouldn’t go so far as tiny) controller
with all surface-mount components. The Parts List
provided is for this version. If size is not so important and
you find surface-mount work challenging, you can build a
version like my
prototype which uses
components for the
passive parts and DIP
versions of some of the
ICs if they are still
available (I find this can
I’ve also included a
schematic file ( IR1.sch),
Note that there is a small daughterboard that holds
the micro USB connector for a power input. You can see
May 2016 27
PART DESCRIPTION DESCRIPTOR PARTS/BOARD SOURCE
TSMP77000 IR Detector IC4 1 Mouser Electronics
PIC12F1840 uProcessor IC1 1 “
MCP6402 Op-amp IC2 1 “
MCP42010 Prog Pot IC3 1 “
STPX-3501-3C 3. 5 mm Jack J1, J2 2 “
10118193-0001LF uUSB B Jack J3 1 “
F930J476MBA 47 μf Cap C5, C6, C7, C8, C10, C12 6 “
WP710A10QBC/D Blue LED D1 1 “
CRCW060310KFKEA 10K Resistor R3 1 “
CRCW0603XXXFKEA 4.7K Resistor R5 1 “
CRCW0603XXXFKEA 1K Resistor R1, R2, R4 3 “
GRM188R70J103KA01D .1 μf Cap C1, C2, C3, C4, C9 5 “
EVQ-PLHA15 Tactile Switch SW 1 “
609-3272 Pgm Socket CON1 1 “
IR1 PCBs Main and Pwr PCB 1 View and modify on
075X12/BK Enclosure 1 Standard Injection
ITEM PART SOURCE
Stereo Microscope Sharp SE303-PY AmScope.com
Solder Paste SMD291AX Digi-Key Corp
Solder Flux SMD291NL "
.031" Soldering Tip* E TH "
.015" Solder 82-105 "
Solder Braid CW2-5 "
Tweezers Multiple sources
Hands-free Magnifier Multiple sources
Soldering Help http://store.curiousinventor.com/guides/
*Note that this tip is for a Weller Model WE551; select a similiar tip for your soldering station.
Working with Surface-Mount Parts on the Cheap
The one indispensable item for surface-mounting parts
by hand is a good set of tweezers (see All Electronics
website). Regular long nosed pliers are just too big to
maneuver the tiny parts to place on your PCB.
Another low cost item is a pair of helping hands
w/magnifier (also at All Electronics.) This stand-mounted
magnifier can serve as a low cost microscope for placing
and soldering ICs and passives to your PCB.
For a little more (less than $130 from AmScope), a true
stereo microscope (with at least a 10X range) is a big asset
(also good for checking out bugs).
Some small diameter solder is a must. I use .015"
diameter. Solder braid is one of the best ways to remove
solder bridges across the pins of ICs.
A 1/32" screwdriver tip on your soldering pencil and
some solder flux and paste helps complete the bill to work
with surface-mount parts.
Finally, check out PanaVise ( http://panavise.com), who
is a major manufacturer of precision vises, circuit board
holders, and work holding tools.