February 2017 63
success is knowing and maintaining
the proper time vs. temperature
profile. The temp ramps up, levels
off, and then ramps down all under
processor control. Ryan also refers to
SparkFun Electronics' Reflow Toaster
Controller for toaster ovens. Another
reference is to Kester’s SMD soldering
time/temp profile ( kester.com) and I
plan to read it. You should too.
The second least complicated
method is analog and manual. If you
mount a readily available barbeque
thermometer inside your toaster,
you’ll be able to raise/lower inside
heat and time the temperature
transitions with a watch. I understand
this not-very-fancy-at-all method and
notice my grill’s temp gauge reads
up to 700 degrees F. That’s more
than enough range to see SMD
solder paste melt. My grill’s gauge is
a replacement I bought in the BBQ
section of a local big box store and
is not expensive. Now all I need is
patience and a working clock!
#4 There are circuits to control
a toaster oven to make a reflow
oven, but I get decent results using a
normal toaster oven and the following
1) Mark the top of the toaster
oven with a Sharpie™ that it is never
to be used for food.
2) Use standard tin-lead solder
paste, with a low melting point.
3) Get a stencil to help screen
the paste on your board. OSH stencils
work fine for most hobbyist work (low
4) Once you have placed the
components, put your board in the
toaster oven, and turn it on to bake at
a low temp (~250) and leave for 5-10
min to bake out any moisture.
5) Turn the toaster up to broil,
and keep an eye on the board. You
will be able to see when the solder
melts and begins to flow. I usually
wait 20-30 seconds after I see the
solder begining to flow, then turn off
the toaster oven.
6) Open the door and allow the
board to cool for 5-10 min before
moving it, then take it out and let it
finish cooling on your bench.
[#10164 - October 2016]
iPod Charge Dilemma
I have a USB charger that works
with my cell phone but it won’t
charge my iPod. Is there something
“special” about the Apple iPod
charger and if so, can I modify a
“regular” charger to work with both?
#1 iPods require voltages on the
data pins of the device in order to
charge. If your charger has just the
positive and negative pins connected
to the plug, your iPod won’t charge.
This is probably the case. Search the
Internet for USB charger circuits.
The modification will require four
resistors wired from ground (negative)
to positive as voltage dividers. One
pair for Data + and the other pair
for Data -. According to the circuit
diagram I found, you will need two
27K resistors, a 22K, and a 39K. The
two 27K resistors are wired to ground
(negative) pin 4 on the charger plug.
The 22K and 39K are wired to the
positive pin 1 on the charger plug.
The junction of the 27K and 39K
divider is wired to pin 2 (Data -) on
the charger plug. The junction of the
27K and 22K divider is wired to pin 3
(Data+) on the charger plug.
Also, for an iPod you should have
a charger capable of at least two
amps output. The wimpy one amp
chargers will take a much longer time
to charge Apple devices like an iPod.
To be sure which pins are which, just
do a search for USB pinouts.
#2 In order for the iPod to charge
using any USB charger, you need to
use a small adapter.
Apparently, Apple chargers
have a resistor between the two
data pins inside the charger. I had
a similar issue when trying to use a
non-Motorola or car charger with the
Razor V3M phone. A small adapter
does the trick and makes the device
think a genuine charger is connected.
You can get one here: www.
[#10165 - October 2016]
Arcade Game Restoration
I’m refurbishing a vintage video
arcade game. There is a transformer
between the video monitor and
the mains power but it measures as
open. From the schematic, it seems
to be a simple 115 VAC 1:1 isolation
transformer. Is an isolation transformer
necessary when the entire cabinet is
wood, or is it overkill?
The isolation transformer is for
protecting the MAIN METAL PARTS
of the arcade machine from electric
shock — specifically the coin-handling
mechanism. If you’re not going to
use the coin machinery (i.e., replace
it with a switch or similar), then you
could probably get away with not
using the line isolation transformer.
HOWEVER, consider integrating
EMI/RFI/surge protection on the AC
power input to help the machine live
a little bit longer.
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