This is only a preview of the April 2021 issue of Practical Electronics. You can view 0 of the 72 pages in the full issue. Articles in this series:
|
DIY Solder
ReFLow Oven
Part 1
by
Phil Prosser
with PID Control
Make short work of soldering boards full of surface-mount components
with this low-cost and easy-to-build DIY solder reflow oven. It’s quite
cheap to build but it runs your PCB(s) through a temperature profile much
like a professional reflow setup costing thousands! It can also be used
to ‘bake’ components, cure glue or paint, or any other task where you
need to hold something at a stable, elevated temperature for some time.
T
here are several reasons that SMD components
are becoming so common, to the point that it’s becoming very difficult to avoid them.
It is due to the need to make products ever smaller, and
the lower cost of mass manufacturing these parts and the
boards that use them. As a result of these and other factors, most manufacturers do not release new components
in anything but surface-mount packages.
If you have young eyes, a microscope or good magnifying glass and some patience, this is not such a problem. So
while we are conscious that surface-mount devices (SMDs)
16
present a challenge to some, we use them where we need
to. However, some of the smaller packages present a real
challenge, especially those with thermal pads in the middle
of the device, and leadless packages to name a (very annoying) few! These cannot be soldered with a regular iron.
If you see yourself building projects with SMD parts and
especially the pesky ones that do not lend themselves to
hand SMD soldering techniques, then this project is for you.
Alternatively, if you are looking for a simple way to
control the temperature of an electrically heated oven, this
is also a very handy device for that job.
Practical Electronics | April | 2021
Working with SMDs
We have, at times, used a hot-air blower on a device, to heat
it and the board until a thermal pad under an IC reflows.
This generally works, but it’s a bit of a hit-and-miss
method, requires quite a bit of skill, and can regrettably
lead to the demise of expensive chips!
Not only that, but a hot-air blower invariably tries to
blow the SMDs out of position!
In commercial manufacture, these devices are generally
‘reflow soldered’ in one form of oven or another.
This project presents a more controlled alternative to our
brute force methods. It follows in the footsteps of others
who have repurposed a toaster oven as an SMD reflow oven
(do see Mike Hibbett’s Beta Layout’s Re-flow Oven Kit and
Controller review in our April 2014 issue).
What is reflow soldering?
Reflow soldering is a process where solder paste is applied
to the pads on a PCB, the SMD components are loaded
onto this paste, and the entire PCB goes into a reflow oven.
This subjects the board to a temperature profile that heat
soaks the components, then briefly bumps the temperature
up to melt and ‘reflow’ the solder paste.
The entire process in a commercial environment is
automated, with robots loading the components and the
reflow oven having sophisticated thermal control and the
ability to ramp the temperature up and down from the
reflow point very quickly.
While that’s nice, you don’t need all that complicated a
rig to get a good result. This project repurposes a regular
toaster oven to allow you to reflow one or several boards.
We are using tin/lead solder, and recommend that you
use this too, due to its lower temperature requirements. It
may be possible to use such a rig with lead-free solder, but
we haven’t tried it.
This allows you to solder pretty well any SMD to a PCB,
and to handle those pesky devices with heat spreaders and
LCC packages. It works just as well for your usual resistors,
capacitors and semiconductors. And the great thing is that
you can solder many components at once; a whole board
(or even a few) is possible, depending on the design.
We should point out here that some board designs may
not be suitable for reflow soldering.
It’s generally best to have a consistent amount of copper across the PCB to use this technique. A board with a
large ground plane on one side and sparse tracks on the
other will not heat evenly, and so you could end up with
unmelted solder paste at one end, or in the worst case, a
burnt PCB at the other!
Having said that, a great many SMD-populated boards
can be soldered in a reflow oven. So it’s a very useful tool.
The simple method
With a stopwatch, a K-type thermocouple and some practise, it is possible to work out an ‘on/off’ timing sheet that
you can use to reflow SMDs manually. But this is a bit hit
Features
n Self-contained controller converts a toaster oven into
a reflow oven
n Temperature profile follows standard reflow soldering
profiles closely
n Closed-loop PID (proportional-integral-differential)
temperature control using a thermocouple and solidstate relay
n Can hold oven temperature at any point in the range
of 20-230°C (eg, for ‘baking’ components or curing
paint/glue)
Practical Electronics | April | 2021
What is ‘PID’ control?
There are many ways to control a temperature. The simplest
is to switch the heater on if the target is below the setpoint,
otherwise, switch it off. This is sometimes called ‘bang-bang’
control; it is either flat out or off.
This works, but is subject to errors and lots of overshoot,
as it does not consider how far the sensed temperature is
from the setpoint, nor how fast the temperature is approaching the setpoint.
A proportional/integral/differential (PID) controller addresses
these shortcomings. It has parameters for:
• Proportional control, ie, linearly related to the difference
between the two temperatures.
• Differential control, ie, how fast the temperature is changing;
this affects how hard we drive the temperature. This uses the
rate-of-change of temperature to minimise overshoot.
• Integral control, ie, looking at how much the sensed temperature missed the target. We integrate the error in temperature and feed this into the algorithm to ‘trim’ the error
out long-term.
This seems complex, but don’t worry. The supplied software
handles all the details, and comes with a good initial set of
parameters which give you a decent starting point.
The main reason we’re using PID control is to minimise temperature overshoot. The toaster oven has a lot of thermal mass,
as does the heating system, so it is slow to respond.
Once the element has been on for a while, after you switch
it off, the temperature keeps rising for quite some time. This
makes a ‘bang-bang’ controller very prone to overshoot. The
differential term in the PID controller helps us tame this.
Despite this, it’s likely that your oven will still experience
some overshoot. This can happen for several reasons; it may
be that the PID parameters used are not ideal, but the fact is
that the parameters can really only be tuned properly for a
single temperature.
Given that it’s crucial to avoid overshoot at higher temperatures, you’re more likely to experience it at lower temperature
set points.
The controller’s user interface lets you adjust the PID variables
to tune the controller for various ovens. Inside our controller
software, we have put modifications into the PID controller
settings that reduce the drive and increase the damping for
temperatures below 100°C, in an attempt to mitigate the aforementioned low-temperature overshoot problem.
We also disable PID control for the last ‘reflow sprint’, to get
this over with as quickly as possible.
The result is that the errors are relatively small; certainly, a
lot less than a ‘bang bang’ controller would produce.
and miss, and if you have a moment of inattention, things
can come unstuck.
This project takes the guesswork out of using an oven
for reflow, and the controlling computer should not have
any moments of inattention!
This project uses hardware which was previously used in the
DSP Crossover (Jan-Mar 2020). However, the firmware loaded
into the PIC32 microcontroller is, naturally, quite different.
The code is available for download from the April 2021 page
of the PE website; the PCBs are available from the Practical
Electronics online shop.
Most of the other components should be easily obtainable
from your favourite parts supplier, although there are a few specialised components whose sources are shown in the parts list.
17
PID REFLOW OVEN CONTROLLER
USER INTERFACE
THERMOCOUPLE
AMPLIFIER
ROTARY
ENCODER
PUSH
BUTTON
OVEN CONTROLLER
(PIC32MZ)
CON10
CON8
128 x 64
PIXEL LCD
K TYPE
THERMOCOUPLE
TTL
CONTROL
CON5
9V DC
230V
MAINS
INPUT
SOLID STATE RELAY
(OPTO ISOLATED)
SWITCHED 230V
TOASTER OVEN
Fig.1: a block diagram showing the basic operation of the DIY reflow oven. The oven temperature is sensed by a
thermocouple placed within, and this is fed back to the PIC-based controller board via a thermocouple amplifier.
It then controls the temperature by switching the oven element on or off via a mains-rated solid-state relay (SSR).
What is it?
I have designed a proportional-integral-differential (PID)
controller which oversees the oven heating, with user-defined heat soak and reflow temperatures. I have determined
the PID coefficients that work for my test oven, but they
are ‘tunable’ for your oven (you may find that my values
work fine). The basic configuration of the device is shown
in the block diagram, Fig.1.
The control block at left is built using a PIC32MZbased microcontroller board that we have used in two
projects already (more on that later). It senses the oven
temperature using a K-type thermocouple and a prebuilt
thermocouple amplifier module. A solid-state mains relay
controls the oven heating elements, and it’s rounded off
by an LCD so you can see what’s going on, and a basic
power supply.
In the development process, I pulled a couple of ovens
apart intending to integrate the controller into the oven
itself. This is definitely possible, and experienced constructors may take this approach.
But for this project, we have chosen to present a standalone controller for a few reasons.
First, once you are inside the oven, you are presented with
a lot of exposed live parts, and every oven will be different, so it’s difficult for us to describe how to do this safely.
Secondly, there is generally no insulation between the
oven wall and the equipment space behind the controls.
Typical PVC wiring is rated to 70°C.
While some types of wire can operate at higher temperatures, they still cannot withstand the temperatures at
which the oven operates.
So you would have to choose carefully where to mount
the controller, and insulate it thoroughly against heat.
Note that oven manufacturers use fibreglass-insulated wiring and crimp/weld connections exclusively. This is a good
choice for an oven but not conducive to DIY modification.
So we decided to leave the oven completely unmodified.
One of the nice features of this controller, besides the
ability to follow a reflow-soldering profile, is the ability
to accurately bring the oven up to a set temperature and
hold it there. Now that I have this feature, I often use it for
curing paints and glues at 60°C.
If you recall your chemistry lessons, for every 10°C (or
10K) increase in temperature, chemical reactions typically
18
SC
2020
double in speed. I’m impatient, so using the oven to fastcure paints and glues is hard to resist!
Note that many SMDs also require you to bake them at a
particular temperature for a particular time before soldering
if their packages have been open for more than a few hours/
days/weeks. This is usually printed on the packaging. This
oven is ideal for doing that too.
Limitations
There are one or two limitations that we have accepted in
this project:
n The choice of oven limits the temperature ramp rate. We
chose a 1500W oven, and it works well. We recommend
that you use an oven with a similar power rating.
n Convection ovens are a touch more expensive. We tried
both and found convection ovens to be a better choice,
but not by enough to recommend that you spend the extra
cash. One limitation of a convection oven is that, unless
you modify the oven, when we switch the element off,
the convection fan also switches off.
n We have not built a ‘door opener’. At the end of the reflow cycle, professional ovens cool the board reasonably
quickly. In this project, you need to open the door of the
oven a crack yourself. This results in a cool-down that is
remarkably close to the recommended temperature profile.
One advantage that we did note when using convection
ovens (which are basically toaster ovens with fans) is that
they have reduced overshoot at low temperature settings.
That is not a big deal for SMT reflow but makes a surprising
difference if you’re running the oven at lower temperatures,
like 60°C, for drying paint or curing glue.
However, to get this benefit, you need to modify the
oven so that it has a separate mains supply for the fan, to
allow it to run all the time and not just when the heating
element is on.
Because of the safety implications of doing that, we
suggest that only experienced constructors with plenty of
mains wiring experience take on this job.
The overshoot on a non-convection oven going from 20°C
to 60°C is about 10°C, while for a convection oven with the
fan wired to run constantly, it is closer to 3°C. Setting the
PID parameters to avoid this with a non-convection oven
would result in super-slow heating times.
Practical Electronics | April | 2021
Safety
This project has been developed to
minimise the amount of mains wiring
that you need to do. The only mains
wiring we need to do is to connect the
solid-state relay in the controller to a
dual IEC mains socket.
All other parts of this project operate from a 9V plugpack, so most of the
assembly work is easy and safe.
Choosing an oven
We bought the toaster oven shown here
from a general household retailer. You
need an oven with manual control, a
mechanical timer, dual elements (top
and bottom), a minimum power of
1500W, with no LCD or other electronic controls.
If you can get a convection oven that
matches these requirements without
spending much more money, then do
so. Our oven cost around £40. If you feel
tempted to spend much more than £60,
check yourself, as you might be buying
something beyond what is needed.
The thermocouple
Thermocouples are the ‘go-to’ device
for measuring high temperatures.
Thermocouples rely on the thermoelectric effect of two dissimilar metals
in contact. A K-type thermocouple has
wires made of chromel (nickel/chromium) and alumel (nickel/aluminium/manganese and silicon). These
are standard and very interchangeable.
They work to well over 1000°C, plenty
for this application.
A thermocouple amplifier interface
module is also needed. It converts the
tiny voltages the thermocouple generates to a higher voltage that we can
measure with the PIC. It also performs
‘cold junction’ compensation.
Just as the thermocouple generates
a voltage from the dissimilar metal
junction at its tip, it also generates a
voltage where the chromel and alumel
wires join our controller. The thermocouple amplifier has a built-in compensation for this (which depends on
its own temperature).
This meant that if you need the ultimate precision, you will need to connect the thermocouple wires straight
to the thermocouple amplifier, and not
use plugs as shown in our project (Jaycar also has a thermocouple without
the plugs, Cat QM1823).
But we think this compromise is acceptable because the error from using
the plugs and sockets is small.
Incidentally, the thermocouple amplifier we used has a purple PCB. If you
search ebay or AliExpress for ‘AD8495’,
then you should be able to find one
which looks like ours. Note though that
some of these devices come with the
Practical Electronics | April | 2021
This is to whet your appetites ready for next month (when we’ll assemble the
components into the case). Note: this photo was taken before the Presspahn safety
shield was installed. For your continued health, it must be included!
wrong reference voltage; we’ll explain
later how to fix that if it happens.
We want a board that uses a 1.25V
offset for 0°C. If yours is 2.5V instead,
it will not work. The simple fix for this
is short the AD8495 reference pin (pin
2) to ground (pin 3), effectively making
the reference 0V.
The SSR
We used an Altronics S4416A solid
state relay, rated at 40A. This is ideal,
although a 20A mains-rated SSR
would theoretically be sufficient.
The other thing to check for is to
make sure that your SSR (like the Altronics one) will work with a 3.0-3.6V
control voltage. Our PIC will drive it
with a nominal 3.3V DC to switch it on.
The controller
The controller is based the same 32-bit
PIC microcontroller board, LCD screen
and set of controls that we used previously in a couple of projects.
Namely, these are the DSP Active
Crossover and 8-channel Parametric
Equaliser (January-March 2020); and
Low Distortion DDS Signal Generator
(February 2021).
The controller module is a lot more
powerful than needed, but takes advantage of the graphical user interface
(GUI) that I already created for those
projects, along with other storage and
control code. So, it saved a lot of development time, and you at least get
a nice user interface.
To this, I added a K-type thermocouple amplifier I bought from ebay for
less than £5 including delivery, along
with a 40A solid state relay (SSR).
With these few additions, we have
ourselves the makings of a pretty capable oven controller.
The CPU board circuit is shown in
Fig.2. We won’t describe this in great
detail, partly because we already
described it in the February 2020
issue but mostly because, despite
appearances, it’s relatively simple.
It consists mainly of microcontroller
IC11, two crystal oscillator circuits,
an EEPROM chip, a simple power
supply and a bunch of connectors for
routing signals.
The main change is in the firmware,
which has been modified to implement
the temperature control loop and to
provide a real-time display of the
temperature profile achieved.
The overall function of the resulting controller is simple. In operation
mode, the microcontroller reads the
temperature about 10 times a second,
and averages this over half a second.
Every half-second, the PID control
parameters are updated and the controller decides whether to switch the
oven on or off.
See the accompanying panel for a
description on how PID temperature
control works.
In setup mode, you can save the settings, alter the PID parameters, set the
temperatures for heat soak and reflow,
or set the thermocouple temperature
coefficient and offset.
Fig.3 shows what’s on the front
panel control board that connects
19
Solder Reflow Oven
Fig.2: the circuit of the control board. 32-bit microcontroller
IC11 derives its internal clock from 8MHz crystal X2 and
has numerous supply bypass capacitors. It runs from a
regulated 3.3V supply provided by adjustable low-dropout
regulator REG2. EEPROM IC12 is used to store the settings
(eg, PID parameters, temperatures settings). The graphical
LCD is connected via CON8, the front panel controls via
CON11 and the thermocouple and SSR via CON10.
20
to the CPU board via a ribbon cable. Rotary encoder RE1
(with integral switch) and switch S1 allow the user to step
through menus, select options and alter values.
Switch S2 is only needed if an encoder is used without
an internal switch. The capacitors are for debouncing while
the resistors, two of which are omitted, tell the CPU what
type of encoder was used.
Practical Electronics | April | 2021
Construction
The first job is to assemble the PIC32 microcontroller module. Its PCB overlay diagram is shown in Fig.4. Use this
as a guide to which parts go where on the 60.5 × 62.5mm
PCB, which is coded 01106193.
Start with IC11, the 64-pin SMD microcontroller (it
sure would be handy to have a reflow oven at this stage,
Practical Electronics | April | 2021
wouldn’t it!). Make very sure that it is oriented correctly
before soldering its leads.
The required HEX file (2910420A.HEX) is available for
download from the April 2021 page of the website.
You program the PIC using a PICKit 3 programmer once
the board has been assembled (see Fig.10 for the slightly
unusual wiring required).
21
4.7k
R1
4.7k
R2
S2
SELECT
S1
EXIT
TO PORTE
CON20
3.3V 1
5
PS0
PS1
ROTARY
ENCODER
4
B
COM
2 A
3
2
2
3
4
5
6
7
8
9
10
1
RE1
(PS0 & PS1
NOT PRESENT
ON ALTRONICS
ENCODER)
4.7k
R3
4.7k
R4
22nF
22nF
FOR ENCODER TYPE 1 (Simple Grey Code per click): FIT R3 & R4
FOR ENCODER TYPE 2 (One complete cycle of Grey Code per click): FIT R1 & R4
FOR ENCODER TYPE 3 (Three changes in phase per click): FIT R2 & R3
SC
Solder
Reflow
Oven oven
solder
reflow
20 1 9
FRONT PANEL CIRCUIT
Tack down a couple of pins and make sure that all of its
pins are correctly located over their pads before applying
flux paste and soldering the rest. Solder bridges are almost
inevitable if hand-soldering, but these can be cleaned up
with the application of more flux paste and some solder
wick. Follow with the other SMDs, making sure that IC12
and the diodes are oriented correctly. (You don’t need to
fit CON6 for this project.)
Next, fit the through-hole components; don’t get REG2
and REG3 mixed up and note that REG2 now has a small
flag heatsink fitted. When mounting X2, if there is any
chance of the bottom of its metal package shorting to
components below, fit an insulating washer underneath.
CON12 can be left off.
You can now move onto building the front panel control
board. Its overlay diagram is shown in Fig.5. The PCB is
coded 01106195 and measures 107.5 × 32.5mm.
There isn’t a lot to assembling it; if you’re using the
recommended Jaycar SR1230 rotary encoder, besides that
part, you just need one pushbutton (S1), two capacitors,
two resistors (R2 and R3) and header CON20. The capacitors and CON20 are mounted on the underside, with the
caps laid over.
We bought our
K-type thermocouple on ebay for
just over a pound –
including postage!
Fig.3: the components shown here
mount on a front-panel board that
allows you to control the unit. Rotary
encoder RE1 and pushbutton S1
connect back to the control module via
CON20. S2 is only required if you use
a rotary encoder without an internal
switch. The capacitors debounce the
rotary encoder signals.
The
assembled
control board,
ready for installing
in the case. As noted
below, some connectors are
not used in this project.
Now is also a good time to solder the two headers to the
small board coded 01106196 which measures 51 × 13mm,
shown in Fig.6. The SIL header goes on one side and the
DIL header on the other. Then solder its SIL header to the
LCD module, with this board mounted on the back.
Next, make up the two ribbon cables. One has 20 wires,
and one has 10 wires. They are the same length; see Fig.7 for
details. Cut each section of the ribbon cable to length, leaving
around 5cm extra in each case for crimping to the connectors.
You can strip these cables out of ribbon cables with more
wires, by making a small cut between two wires and then
separating the sections by pulling them apart.
The front panel components (as per the circuit of
Fig.3) ready for assembly into the case as seen earlier.
22
Practical Electronics | April | 2021
560VR1 10k
K
LED
2
10 F
DSP SPI1
CON6
20 19
8MHz
LK2
470 F
1
2
1
47
+
GND
REG2
A
V2.0, 2019-03-27
User interface PIC32MZ DSP
S1
47
CON8
20pF
* BOTH CAPS UNDER PCB
OR LAID OVER ON TOP SIDE
D16
GRAPHICAL LCD
ALPHA LCD
330
CON5
LK1
GND
D14
10 F
FB12
20pF
X2
CON12
470
1
47
1
CON23 ICSP
X1
470 SD04
100nF
100nF
390 10 F
1.2k
100nF
100nF
330
1
CON10
RDO
IC11
PIC32MZ
2048
EFH064
10 F
REG3
PORTB
20pF20pF100nF
100nF 32768Hz
10k 100
D15
10 F –I/SN IC12
100nF
PORTE
100nF
100nF
1
CON11
1
100nF
CON7
25AA256
1k
100nF
SPI2/I2S
JP5
1k
VEE
CON9
1
+7VDC
Fig.4: use this diagram as a guide when
assembling the control board. It’s easiest
to fit the SMDs first, starting with the ICs.
Watch the orientation of the ICs, diodes,
electrolytic capacitors and regulators.
Some components are not required for
this application, including CON6, CON7,
CON9 and CON12.
S2
RE2
22nF*
22nF*
SILICON
CHIP
4.7k
4.7k
4.7k
4.7k
R4
R2
R1
R3
1
CON20
(UNDER)
RE1
01106195 RevB
DSP Crossover front panel board
Fig.5: the front panel PCB. Note that only one of RE1 (Jaycar SR1230)
or RE2 (Altronics S3350) is fitted and in the case where RE1 is used,
pushbutton S2 is redundant and may be left off. Also, if RE1 is fitted, fit
resistors R2 and R3; if RE2 is fitted, fit resistors R1 and R4.
Fig.6: this small adaptor board
converts the SIL header on the LCD
screen to a DIL header for
connecting to an IDC ribbon cable.
The connectors are mounted on
opposite sides; make sure the pin
1 connection at both ends is at the
same end, as shown.
It’s best to use a dedicated IDC crimping tool for this job,
such as Altronics T1540. You can use a vice, but you have
to be careful to avoid crushing and breaking the plastic
IDC connectors.
Each connector has three parts: the bottom part, which
has the metal blades that cut into the ribbon cable; the
middle part, which clamps the cable down onto these;
and a locking bar at the top that holds it all together once
it has been crimped.
Note how, as shown in Fig.7, the cable passes between
the locking bar and upper part before folding over on the
outside edge and then being crimped underneath.
So with this in mind, slightly separate the three pieces
without actually taking them apart, and feed the ribbon
cable through as shown.
Ensure there is enough ‘meat’ for the metal blades to cut
into, then place it into your crimping tool or vice without
allowing the cable to fall out.
Clamp the three pieces together, gently at first, then more
firmly. The trick is to crimp it hard enough to ensure that
the blades cut fully through the insulation and make good
contact with the copper wires, without pressing so hard
that you break the plastic.
CON21
SILICON
CHIP
(UNDER)
1 CON22
1
If using a vice, it’s best to wedge a piece of cardboard
between each end of the connector and the vice, to provide
some cushioning.
Once you’ve crimped a connector at one end of the
cable, do the one at the other end, making sure that when
you’re finished, the locating spigots will both be facing in
the same direction.
In the second and final part of this project, which will
appear in our May issue, we’ll cover the steps involved in
putting the controller in a case and safely checking that all
is operating correctly.
We’ll also have a list of troubleshooting suggestions
in the unlikely even that you cannot get your controller
to... control!
In the meantime, you can gather all the components, PCBs
and everything else you need.
Don’t forget the oven!
Reproduced by arrangement with
SILICON CHIP magazine 2021.
www.siliconchip.com.au
LOCATING SPIGOT UNDER
1 0 -WAY
IDC
SOCKET
1 0 -WAY
IDC
SOCKET
1x200mm 1 0-WAY IDC RIBBON CABLE
CABLE EDGE STRIPE
LOCATING SPIGOT UNDER
20-WAY
IDC
SOCKET
20-WAY
IDC
SOCKET
1x200mm 20-WAY IDC RIBBON CABLE
Practical Electronics | April | 2021
Fig.7: you need to make two ribbon
cables: one to connect the front
panel to the CPU board, and the
other to connect the LCD. Note the
orientation of the connector tabs,
so that pin 1 is aligned with the red
stripe at both ends. Make sure the
IDC blades are pressed down hard
enough to fully pierce the insulation
and make good contact, but not so
hard that you crack the plastic!
CABLE EDGE STRIPE
23
Dimensioned diagrams for drilling this plate, the front and rear panels and drilling/cutting the Presspahn safety shield
can all be downloaded from the April 2021 page of the PE website.
Parts list – Reflow Oven Conversion
1 260 x 190 x 80mm plastic instrument case [Altronics H0482]
1 200 x 115mm sheet of 1.5mm-thick aluminium
1 205 x 185mm sheet of Presspahn or similar [Jaycar HG9985]
1 K-type thermocouple with banana plugs [Jaycar QM1284]
1 AD8495-based K-type thermocouple interface with purple PCB
[eBay/AliExpress]
1 populated PIC32MZ CPU board – see below
1 populated front panel control board – see below
1 128 x 64 pixel graphical LCD with 20-pin connector
1 10A dual (male/female) chassis-mount IEC power connector
[Altronics P8330A]
1 9V DC 2/3A regulated plugpack with 2.1mm inner diameter
plug [Altronics M8923]
1 2.1mm inner diameter chassis-mount barrel socket
[Altronics P0628]
1 red binding post/banana socket
[Altronics P9252, Jaycar PT0453]
1 black binding post/banana socket
[Altronics P9254, Jaycar PT0454]
1 double-sided PCB, coded 01106196, 51 x 13mm
1 40A 24-240VAC solid-state relay (SSR1) [eg, Altronics S4416A]
1 SPST, SPDT or DPDT 12V DC, 1A toggle switch (main power
switch)
1 IEC C14 male to 3-pin mains socket [Jaycar PS4100]
1 IEC mains power cable [Jaycar PS4106]
1 15x2 pin header
1 20-pin header
2 20-pin IDC line plugs
3 10-pin IDC line plugs
1 small tube of neutral-cure silicone sealant
1 small tube of heatsink (thermal) paste
Cables and hardware
4 M3-tapped 15mm nylon standoffs
8 M3-tapped 10mm nylon standoffs
25 M3 x 15mm panhead machine screws
25 M3 x 6mm panhead machine screws
25 M3 star/lock washers
10 M3 hex nuts
8 5mm red eyelet crimp connectors
[Altronics H2041A]
1 20cm length of three-core 10A mains flex
1 50cm length of red light-duty hookup wire
1 30cm length of black light-duty hookup wire
1 30cm length of green light-duty hookup wire
1 25cm length of 20-way ribbon cable
2 25cm lengths of 10-way ribbon cable
1 6cm length of 40-50mm diameter clear heatshrink tubing
24
1 50cm length of 10mm diameter clear heatshrink tubing
1 30cm length of 8mm diameter clear heatshrink tubing
cable ties as required
PIC32MZ CPU board parts
1 double-sided PCB coded 01106193, 60.5 x 62.5mm
1 2-way mini terminal block, 5.08mm spacing (CON5)
5 5x2 pin headers (CON7,CON9-CON11,CON23)
1 10x2 pin header (CON8)
2 3-pin headers (LK1,LK2)
1 2-pin header (JP5)
3 shorting blocks (LK1,LK2,JP5)
1 ferrite bead (FB12)
1 32768Hz watch crystal (X1)
1 miniature 8MHz crystal (X2) OR
1 standard 8MHz crystal with insulating washer (X2)
1 10kΩ vertical trimpot (VR1)
1 TO-220 flag heatsink (for REG2) [Altronics H0630]
Semiconductors
1 PIC32MZ2048EFH064-250I/PT 32-bit microcontroller
programmed with 2910420A.HEX, TQFP-64 (IC11)
1 25AA256-I/SN 32KB I2C EEPROM, SOIC-8 (IC12)
1 LD1117V adjustable 800mA LDO regulator, TO-220 (REG2)
1 LM317T adjustable 1A regulator, TO-220 (REG3)
1 blue SMD LED, SMA or SMB (LED2)
3 LL5819 SMD 1A 40V schottky diodes, MELF (MLB)
(D14-D16)
Capacitors
1 470µF 10V electrolytic
5 10µF 50V electrolytic
11 100nF SMD 2012/0805 50V X7R
4 20pF SMD 2012/0805 50V C0G/NP0
Resistors (all SMD 2012/0805 1%)
1 10kΩ
1 1.2kΩ 2 1kΩ
2 470Ω
1 390Ω
2 330Ω
1 100Ω 3 47Ω
1 560Ω
Front panel control board parts
1 double-sided PCB coded 01106195, 107.5 x 32.5mm
1 5x2 pin header (CON20)
2 4.7kΩ 1/4W through-hole resistors
2 22nF through-hole ceramic capacitors
2 PCB-mount snap-action momentary pushbuttons (S1,S2)*
[Jaycar SP0721, Altronics S1096]
1 3-pin rotary encoder (RE1/RE2) [eg, Altronics S3350 or
Jaycar SR1230 with integrated pushbutton]
1 knob (to suit RE1/RE2)
* only one required if using Jaycar SR1230 encoder
Practical Electronics | April | 2021
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