I put together a v6.3 (RDTC) board today and took pics along the way, I will attempt to put together a bit of a build guide here as requested. There are many ways to go about this, you could use solder paste and a hot air soldering gun or a reflow oven, or specialty small soldering tools etc, this guide will cover how you can do it with average stuff you can get at a radio shack type store.
Before I begin the build I should note on V6.3 we added a space for a Standard Pit Probe jack. This means you can use this board without any of the SMD components installed to wire a Roto Damper for a Standard Pit Probe, Two Food Probes and CAT5 jack, as well as connect the blower and servo using the header on the RDTC board. So you can use this board as an alternate to the hand wiring method using the punch down CAT5 jack from Home Depot. It will cost more but is easier to assemble.
First thing to do is clean up the board. When you receive the board from OSH Park there will be little sections on the edges from where the boards were attached for manufacturing. You should clip/file/sand them way until the edges of the boards are even, as shown in the board on the bottom in the following picture. If you don't do this they may interfere with fitting the board in its case (btw, you should do the same on your HM board before you build it)
Here is a pic of the tools I used to do the assembly. A standard Weller 25 Watt soldering iron, thin solder, solder wick, and flux, as well as some tweezers and a pick to help with placing the very small SMD components. I also wore a magnifying visor that I got from Harbor Freight for about $3 bucks so it was easier to see when working.
I put a thin coating of flux on the board and then placed the TC amp IC in place, noting the dot on the board and the IC which is in the upper right corner in the picture below (though not visible at this resolution). After I lined up the IC on the board I soldered one corner leg in place, which you can see in the following picture. After you tack down this one leg make sure the IC is still aligned, if not then reheat the leg and nudge the IC into position.
If you have a very fine soldering iron tip you can attempt to solder one leg at a time and do it cleanly (without creating solder bridges to the adjacent legs). I have done it before but it is extremely difficult. I find it easier not to worry about the bridge, I still solder each leg individualy and try not to flow too much solder to each leg, but don't worry too much about the invitable bridge across all 4 legs as shown in the pic below:
It usually works out quite easily to remove the solder bridge and excess solder using solder wick as shown in the pic below. I first dip the wick in flux (and wipe leaving a thin coat over the entire braid) then place the braid across all 4 legs of the IC. Press the soldering iron down on the braid somewhat horizontal across the IC legs and the wick will get hot, flux will melt and the excess solder will be drawn up from the IC legs. In the picture below you can see the top row of legs has been cleaned up in this manner already, and have things in position to do the bottom row.
After you get all the SMD components soldered on the board you can test the TC amp with the same procedure detailed in the HM build guide. I tend to prefer doing a quick continuity test on the IC after I have done the soldering and cleanup, making sure the IC legs have continuity to the right places and there are no shorts between the legs. Below is a pic of the RDTCv6.3 board that I have added a color code to, showing the nearest direct connections to each IC leg. You can use this to make sure the IC legs are soldered well to the board and having continuity to the nearest connected component, and you can also use it to make sure the adjacent IC legs are not shorted to each other. It's easier to test for shorts between the legs using the larger solder pads for resistors/caps that have the same color as shown on the IC legs (instead of trying to put meter leads on two very tiny legs right next to each other on the IC). Note that two legs (yellow) are connected together (bridged by a trace on the board), and the one leg with the X on it is not used, so you don't have to worry about bridges in those places.
After the IC is installed and tested as above it's time to install the SMD Caps and resistors. I did them in this order:
3X .1uf caps
2X 1nf caps
1X 10nf cap
2X 10K resistors
1X 1K resistor
1X MCP1700 3.3v Regulator
1X 1M resistor (Optional, only if installing REF offset circuit)
I find it easiest to place the parts with tweezers, when oriented properly press them down on the board a bit, this seems to help hold them in place a bit (they kinda sink into the flux that is on the board). Then I lightly solder one side of the component, if it moves out of place reheat the solder and use the pick or tweezers to push the part into place, let that solder cool briefly and then solder the other side of the component. Here is a shot of the board with all the SMD parts in place.
The board looks a mess with all that flux, particularly with all the reflection in a picture, but it cleans up really nice with a little isopropyl alcohol and a soft bristle brush.
The TC circuit on the HM bottoms out around roughly 37F, so the HM will just flat line at 37F no matter how cold the TC gets. If you live in an area where it gets sub zero and want your TC to have the ability to measure lower temps you can install the REF Offset Circuit. I should note, the HM/RDTC will function fine without the REF Offset circuit even in sub zero weather, you will just not be able to see the actual temperature when it is below 37F.
The REF Offset circuit consists of the OP777 Op Amp, the 1M resistor, and the trimmer potentiometer. The OP777 IC is on the other side of the RDTC board. It has a bit more space between the legs than the TC amp so it is much easier to solder, you shouldn't have any problem getting this done without solder bridges. Note the dot on the lower right corner of the part and on the board for orientation. Here's a pic of the OP777 installed.
With the REF Offset circuit installed, when the trim pot is fully counter clockwise the TC should read actual room temperature, as you rotate the trim pot clockwise you will see the temperature reading on the HM for the TC rise upward a bit over 100F at max. To set the offset decide how low you need the TC to register first. If you want the TC to register to 13 below zero, for instance, use the REF Offset Trim Pot to raise the TC temp 50F (37 + 13) and then in the HM Config for the TC set an offset of -50F. After you change the offset setting in the HM config the TC will show proper room temp and will now register temps down to 13F below zero. (50F below the normal low end reading)
If you are not installing the REF Offset circuit you can omit those parts and just make a solder bridge across the solder pads labeled REFG. Also note, if you are not using the REF Offset circuit you don't have to worry about cleaning up a solder bridge between the green and purple legs of the TC amp IC.
That covers all the SMD work on the board, I will continue in the next post with installing the larger pieces of hardware to finish the board. (I have hit the limit of pics I can include in this post)
thanks
