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PLT 1002 Wireless Temperature Sensor


First, check you have all the components for the PLT-1002.













Three colours




Short button




Long button





C1 C2 C5



100nF (labelled 104)

C3 C4



22pF (labelled 22)

R1 R2 R4 R7



10k (Brown Black Orange Gold)

R3 R5 R6



330R (Orange Orange Brown Gold)







Temperature Sensor



Male breakaway header for ICSP, Serial,Power, Breakout connections

Solder wick

Printed Circuit Board (PCB)

What you’ll need

A soldering iron.  There is a small amount of surface mount soldering in this kit.  You don’t actually need one with a 0.2mm tip, or even anything like it. A “normal” soldering iron you’d happily use for through-hole components will be fine. It’s a little easier with a thinner tip – you can place heat more accurately – but that actually brings some more challenges, since most irons with a thinner tip don’t actually get all that hot right at the tip, so you end up using the side of the tip anyway.  The tip does need to be shiny and hold solder on it when you melt solder on to it.

You’ll need a wet sponge to clean the tip with regularly.

Wire cutters.  To clip the ends of components after they’ve been soldered.

A well-ventilated area in which to carry out your work.  Even if you’re doing the right thing and using lead-free solder, we recommend working in an area with plenty of air flow.

A multi-meter is always handy as you hook things up.

Surface Mount Components

The first thing to solder is the surface mount components, simply because it’s much easier before all the other components are fixed in place.

Start with the TMP75.  Apply a little solder to one pad on the printed circuit board where the TMP75 is to go, such as pin 1 (indicated by a dot).

Using tweezers or similar, place the TMP75 chip on the PCB.  Note that the TMP75 may indicate the end of the chip where pin 1 is by a bar instead of the more usual dot. So the end with the bar goes towards the inside of the board.  While holding the TMP75 in place, head the solder you have already applied with your soldering iron so it becomes molten. Use the tweezers to arrange the TMP75 in the right place at the centre of the SMD pads.  If you don’t get it right first go, take your time and simply re-head the pad until you have it placed correctly.  Make sure the pins are centred in the middle of the pad and the chip itself has about the same amount of pad exposed on either side.

Moving to a pin on the other side and other end of the TMP75, clean your iron tip on a wet sponge and then apply a small amount of solder to the pin and pad.  It will need a moment for the solder to “take” to the pad. Don’t worry too much if you bridge two pins with solder, so long as they are both affixed to their pad.  Keep doing this until you have all pins soldered down.

Now inspect your chip carefully to see if you have in fact bridged any pins.  If you have, first clean you iron tip, then try melting the solder in between the pins with your iron tip, then sliding the iron back down the pins away from the chip.  If that doesn’t clear it, it’s time for one of the greatest inventions known to soldering: solder wick.

We’ve included some in the kit.  Make sure the wick has a nice clean end, cutting it if necessary.  Holding the wick with one hand and your iron with the other, place the end of the wick on the pins you need to clear.  Place the iron on the wick so the wick is sandwiched between the iron and the pins. Holding it there for a moment, you should find that the solder melts and the wick soaks it up.  As you remove the solder, don’t forget to take the wick with it – otherwise it will end up stuck to the pins.  Now check the pins – you can add more solder now if you wish, but you’ll probably find that the pins are actually still soldered down.

Continue until you have removed all extraneous solder.  Don’t forget to clean your iron tip and make sure you cut off the used wick before you do the next one. If you find nothing’s happening, you have probably forgotten to trip your wick.

Use the same procedure with the PIC.  Melt solder on one pad and use it as an anchor to hold the PIC in place.  It’s actually slightly easier, since you can hold it down with a finger instead of using tweezers, but we find it is easier to practice with chips with less pins.  Don’t worry, after doing a couple of surface mounted chips, it will all seem straight forward.  Armed with solder wick, there’s not too much you can’t fix.

If you’re using an MRF24J40MB module, now’s good time to solder it as well using the same process.  By comparison it’s a piece of cake with such relatively enormous “pins” and pads.  You can solder it later if you don’t have a module to hand.


Resistors R1, R2, R4 and R7 are 10k Ohms.  They’re coloured Brown Black Orange Gold.  Bend them into shape and solder them on the other side.  Clip the leads when you’re done.

Resistors R3, R5 and R6 are 330 Ohms, indicated by the colours Orange Orange Brown Gold.  Solder them next and clip.


Diode D1 is a 1N4148.  Bend into shape, solder and clip, keeping the stripe on the diode the same direction as the one on the PCB (that is, towards C2).


C3 and C4 are 22pF capacitors.  They’re the smaller ones – and you’ll notice they’re marked with ‘22’ on them in very small print. Solder them next; they go next to where the crystal goes.

C1, C2 and C5 are 100nF bypass capacitors, marked ‘104’.


The 16Mhz crystal is next.  Make sure the crystal has ‘16’ or ’16.000’ marked on it and solder it in the spot for it next to R4.


 You have three coloured LEDs available to you.  We prefer the traditional Red / Amber / Green ordering, with the red LED furthest from the MRF module, but it’s your board so feel free to arrange them how you wish.  Make sure the long lead goes in the hole marked with “+” ; they won’t work the other way around.


It’s time for the switches now.  The reset switch takes the shorter switch and S1 takes the longer switch.  This is simply due to the fact that you only want to reset the circuit when you mean to.  The switches will naturally fit only one of two ways, and either is fine.  You’ll notice there’s plenty of give in the PCB holes for them.  Suspend the switch in place, soldering one leg, make sure it’s flat, then return to the other legs.  As always, it’s best if you use one pin to anchor and position it.  A good trick here is using blu-tack to hold it in place.


Finally, it’s time to solder the male headers in place.  Clip the breakaway header to the right length.  Solder one pin and then check the header you’re soldering is actually perpendicular to the board.  Melt the solder and adjust as necessary.  Once you’re satisfied, solder the rest of the pins.  Repositioning after one pin is easy. After solder two or’s pretty much impossible.

Final checks

 Have a good look at the board.  Look for solder bridges on the surface mount devices and check for nice shiny solder connections on the back of the board.  Check you’ve actually soldered everything too.

Initial testing

 Time to check it actually works.  All our PICs come with the BoostBloader pre-loaded.  So the first thing that should happen after applying power is that LED1 (furthest from the MRF module), connected to RA0, should flash.  This is a very good sign that all is good in the world.

When applying power, make sure you get it round the right way.  Ground goes to ‘GND’, 3V or so goes to ‘+3v3’.   Double check your supply with a multi-meter if you are any way unsure.  This also confirms your supply is working.

If it doesn’t work:

-      Have you got D1 round the right way?

-      Are the LEDs round the right way (long leg down the + marked hole, flat side away from the MRF board?

-      Are there shorts on any of the surface mount pins?

Actually, there’s not much that can go wrong with this kit so long as your soldering is okay.  We don’t really expect you to have any problems here.  Email us at if you’re really stuck.

Updating software

 Fine, you’ve got a LED flash. What next?  Crank up your copy of SourceBoost, compile EA_Wireless_Temp_Sensor (in the projects directory of where ever you’ve put the PicPack library.

Connect your TTL-Serial connection to the Tx/Rx and ground connections supplied on board, noting that you’ll need to swap the Tx/Rx connections (TX/out from the board is Rx/in with respect to your TTL-Serial board).

Now you’ll be able to use the venerable Screamer application (found in the PicPack collection) to send the .hex file produced by SourceBoost to your board.  Select your Com port, set the Speed to 115200, and Oscillator to 64Mhz (this is the speed the chip is running at, 4 x 16Mhz).  Find your .hex file by pressing Open, then press the nearby Download button to transfer the .hex to the PIC.  The first time you do this you may need to press the reset button on the PLT-1002 to get them to sync up.  After that, it should happen just by pressing Download.

For more information about bootloading and BoostBloader, see the Tutorials section on the website.

After that – it’s up to you!  Do send us in any feedback on making our using this kit to  If you’ve had problems, please let us know so we can improve our kits and instructions.  If you’ve had fun, tell us about what you’ve made.