Table of Contents
Building the WiFi 1-Wire Host Kit:
The 1-Wire Host Kit is a through hole soldering kit. For operating and configuration instructions please see this article. The processor is an ESP-01 chip and comes pre-programmed with an Arduino compatible open source firmware that is also digitally signed for security.
- Project Enclosure: optionally a black plastic labeled project enclosure or not shown a DIN rail mounting plate.
- Circuit Board: Depending on the hardware revision your 4 port header may be pre-soldered to the board when you receive it.
- ESP-01: The pre-programmed ESP-01 CPU.
- 8 pin Switching Power Supply Driver.
- 470uf Capacitor
- 100uf Capacitor
- Diode depending on the hardware revision you may have a second diode as well.
- 470pf capacitor
- (2) .1uf capacitors
- 2 pushbuttons
- 3.5mm barrel jack for DC power
- 4 pin removable header
- 4 2.5m phillips or hex mounting screws
- 8 pin ESP-01 mounting header
- 220uH choke
- yellow or blue LED
- .33ohm power supply sense resistor
- 5 more 1/4 watt resistors see below for values
Step 1: Solder Resistors
This project is not meant and not setup to be a basic soldering how to. There are MANY such things on the internet. While this is a simple kit to build if you haven’t got some soldering experience you would be well served by doing some other simpler things prior to tackling this kit!
There are 6 resistors included with the kit, We can place and solder them now.
The most obvious is the .33 ohm sense resistor. This is part of the power supply and lets it measure the voltage drop across a small resistor like that in order to keep the voltage the same at the output. This is the larger blue, wire wound resistor. It should be installed just to the right of the 8 pin chip socket. Being a resistor it has no plus or minus so there is no right side up or upside down.
Just to the right of the sense resistor are three more. From top to bottom they are the 3.3k resistor with color bands of “Orange Orange Red Gold” and then below that the 1.8k resistor with color bands of “Brown Grey Red Gold” and lastly in this row the 4.7k resistor with bands of “Yellow Purple Red Gold.” The first 2 are part of the power supply forming a voltage divider to let it sense the voltage being output to the rest of the board. The 4.7k is delivering power to the data line of the 1-wire bus if you’re running in parasitic power mode.
To the right of those 3 are 2 more running vertically. The first is a 100 ohm resistor with color bands of “brown black brown gold” that is a current limiting resistor to the Status LED. The second is a 10 k resistor with color bands of “brown black orange” which is part of the reset circuitry of the ESP chip to make sure that it powers on properly.
While it is not absolutely necessary it is quite helpful to have a resistor lead former which you can get here: As an aside, the evil mad scientist mentioned in that link and I have been friends since college and I fully endorse his kits and projects and you should build them.
Soldering the Resistors
A resistor does not have an orientation that matters so you can insert them in any way. However if you wish to look at this board years in the future and be happy with your work I recommend aligning the gold bands in the same direction left or right and top or bottom.
If you insert the resistor and then bend the leads out to the sides it will hold the resistors in place as you turn the board over and solder them into place.
The pictured holder for a PC board in progress is not required, but it does make the job of placing components and then soldering them in place a bit easier. Resistors are not particularly heat sensitive so take your time and make sure the solder is flowing properly into and around the connections. You should see a nice dome of solder when you’re done. A “ball” that is floating above the connection is not a good connection nor is a matt whitish flow that is sunken into the hole. If you’re seeing any of these then you should take a step back and do some basic soldering exercises or drop me an email with pictures for help.
While these kits will work with leaded or lead free solder I recommend the leaded kind. It is easier for a hobbiest to work with and will last forever even if you didn’t do the best job while soldering it. I assembled my first alpha clock kit with lead free solder and even though I think I did a great job I have had to touch up cold solder joints every couple of years as they just go bad for no reason. If it is legal for you to use leaded solder in your country and you have it then I recommend that you do so. Here are some leaded solder things to remember:
The smoke from the flux has no lead in it. None, not even enough molecules for it to matter. The smoke is an irritant and may make you wish you had thought to put out a fan to blow it away but it will be the same for leaded or lead free solder. The vapor pressure of lead at soldering temperatures is not high enough for it to fly up into the smoke.
The leaded solder will contaminate your hands. If you have touched anything made of lead please wash your hands when you’re done.
lead free solder requires that you work at a higher temperature which makes it more possible to damage the components you’re working on. If you are skilled at soldering then you can almost certainly work with lead free solder at least as well as you can leaded solder. If you’re a beginner leaded solder is much easier.
When you’re done remember not to grind up your old projects and eat them. Seriously recycle them with the proper waste stream as we don’t need any more lead in the landfill improperly. I personally have no intention of recycling any of my projects in my lifetime and will hand them down to my children who will know how to deal with them or properly recycle them so I am not worried about the lead in the system. If I was selling hundreds of thousands of pre-made devices then I would use the lead free variety. For a small volume kit I think the argument for leaded solder is compelling.
Once you’ve gotten a solder joint that makes you happy get out your flush cutters and cut just above, or just into the solder ball. Do not try to cut flush with the board as you may damage the traces on the board or pull out the solder joint. It’s OK if they stick down a millimeter or so.
Step 2: Decoupling Capacitors
There are 2 identical 0.1uf decoupling capacitors included in the kit. They are important for keeping transient changes on the power supply lines from looking like level changes internally to the CPU. Polarity does not matter for these so they can be placed any way around. Do not confuse the single 470pf capacitor with these. It is physically smaller and has formed leads. The two decoupling capacitors should be placed as in the picture on the right.
Once placed you can gently bend the leads out to the side to hold them onto the board as you flip it over, solder them and then flush cut the wires.
Step 3: Power Supply Diode and Capacitor
This diode is the first component we’re going to add where orientation matters. Please line up the white mark on the diode with the white mark on the board. If you have a revision 2 board there will be a second identical diode just to the right of this one. Add that one at this time as well. Apart from the orientation issue these solder just like a resistor. Bend the leads out gently, turn the board over, solder and flush cut.
At this point you can also add the 470pf capacitor. You’ll see it’s marked spot just above the diode. Orientation does not matter for this part. The formed leads are not perfectly sized for the holes in the board but it doesn’t matter if it hangs to one side a bit. Or you can straighten out the leads a bit and make it fit perfectly.
Step 4: Power Supply Driver Chip
Now we’re going to add the power supply driver chip. Please pay attention to the orientation as shown in the picture. The small half circle on the chip should be pointing up to match the notch on the silk screen border of the chip.
The leads of the chip will be already formed and bent more or less into the proper orientation to fit easily into the holes on the board, but it may still be necessary to adjust them a little manually to get it to easily slip into the board. Make sure that all the leads pass through a hole. If you have to force it it’s quite possible for one of the leads to roll up under the chip and not go through a hole.
Once you’ve got it placed turn the board over while keeping a finger on the chip to keep it from falling out. If it is not in tight enough to hold it while you solder it you can use a spudger or other tool that won’t damage the underside of the board to bend one or 2 of the leads over.
This chip is the most difficult part to solder so far. The pins are close together and the device is more temperature sensitive than anything so far. As you’re soldering check to make sure that you’re not forming bridges between adjacent pins. I would also alternate soldering from one side to the other in order to keep from overheating the chip in any one spot.
Step 5: Finish the Power Supply
The coil is the black shrinkwrapped device and goes into the spot labeled 220uh on the upper left of the board. It is not polarized so orientation does not matter. Bend the leads out slightly on the back to hold it in place.
There are 2 larger electrolytic capacitors to place now. These are polarized and must be soldered in the right direction. Please note the negative indication on the can of the capacitor and make sure to line that up with the negative marked connection on the board. On the silk screen this is labeled with a small minus sign on each side and the hole itself is square. The 470uf capacitor is yellow in the picture and the 100uf is black, but future parts may be different colors. Don’t be concerned if the lead spacing of these larger capacitors is not perfect with the hole spacing on the board. Don’t force them to be flush with the board if they don’t fit perfectly. They can float a tiny bit above the board to avoid placing too much strain on the leads as they come out of the can. Once they are placed double check the polarity, bend the leads out on the back a little bit to hold them. Turn over the board and solder them both as well as the coil then flush cut the extra leads.
Step 6: Add the ESP-01 Header
Next lets add the socket for the ESP-01 CPU. Please resist the temptation to solder the ESP directly to the board. Being able to remove it means that if a firmware update fails you can always remove it to reprogram it in a programmer or replace it with a new or better device in the far future. This part is the 8 pin in 2 rows of 4, black plastic socket and is placed at the upper right hand of the board. Like the power supply chip this socket also has it’s pins very close together making it harder to solder without bridging the pins. It also will not hold itself onto the board while you flip it over so you’ll have to hold it in place. You can use a piece of tape to hold it in place while you solder it, but I find it is not difficult to hold it with your finger. Make sure you’re holding the opposite side from the side you’re going to solder! If you have some flux you can add a small dab to the first pin you’re going to solder but it’s not completely necessary. Since you are using one hand to hold the socket in place you don’t have 2 hands to hold the soldering iron and the solder. Clean your iron and get a small ball of solder on it. Then hold the iron to the pin furthest away from where you’re holding the underside of the socket. Without flux the solder will not flow properly but you’ll be able to get enough onto the pin and pad to hold the socket in place. Once you’ve done that you can stop holding it and finish soldering it normally. Be sure to start at the opposite side from where you tacked it in place. If you immediately re-melt the only pin holding it in it will just fall out. Then lastly make sure to re-solder properly the pin you tacked it with otherwise that will be a cold solder joint and unreliable.
If you have a revision 2 board without the green removable header pre-installed now is a good time to add that as well. You can use the same technique as with the ESP socket of holding it on one side and tacking the other in place to hold it while you properly solder the others. In this case it’s even more important to make sure you’re holding the opposite side from where you’re tacking as you’re more likely to be holding onto one of the metal pins. If you end up soldering the one you’re touching you’ll give yourself a blister fairly quickly.
Step 7: Pushbuttons and Barrel Jack
Now lets add the 2 pushbuttons for setup mode and reset. These are rectangular and will only fit into the board in one orientation. Though there is no up or down there is a left and right. They will snap into the board and should hold themselves securely while you turn the board over and solder them. The leads are short so there is no need to trim anything.
The barrel jack may or may not hold itself in place. If not you can do the same trick as with the headers and hold it in while tacking it in place with a little solder already on the iron. Then follow up and securely solder the remaining 2 connections and re-flow some more onto the one you tacked. This is one of the connections that can be subjected to a lot of physical force as you plug and unplug the device so make sure to make a good connection. You do not have to fill the entirety of the large holes on the board, indeed you probably shouldn’t as you risk melting the plastic of the plug. But you do need to make sure that the tabs are soldered to the edges of the holes along the entirety of their length.
Step 8: Status LED
The kit will have shipped with either a yellow or blue LED though it might also be a clear case. Orientation matters for the LED The LED has 2 indications of polarity. The circular base of the LED itself has a flattened section that should line up with the flattened section on the silk screen of the board, but more easy to see is that one lead is longer than the other. The longer lead should go through the square hole.
Don’t place the LED flush with the board, but rather insert it so that just a quarter inch or so is sticking out the back and then bend it forward so that it peaks out the front of the board as shown. This will make it easier to see out the bottom of the case once it’s fully put together. Once you have the LED placed to your satisfaction you can solder and flush cut the LED.
Now you’re done soldering!
Step 9: Test the Power Supply
Now lets make sure the power supply puts out the proper voltage for the ESP chip. You’ll need a multimeter for this step set to DC volts. Plug a 5v or 12v adaptor into the barrel jack and measure the voltage between the “3.3v” pin and the “Gnd” pin on the green header. Being careful not to short the two together or either one to the Vin pin. You should measure a solid value between 3.3 and 3.7 volts. If so then you’re good to finish the assembly! If not get out your magnifying glass and search the back of the board for solder bridges and double check the orientation of the large capacitors, the diodes and the power supply driver chip.
Disconnect the power adaptor before continuing!
Step 10: Install the board into the case
Orienting the board properly in the case is important. It will fit over the two large posts in either direction, but only in one direction will the 4 screw holes line up with the board and the connectors line up with the bottom open portion of the case.
Once it’s properly placed you can carefully install the 4 2.5m screws that hold the board securely inside the case. These may have Philips or hex heads. Don’t over-tighten them as it is easy to strip out the plastic threads in the case posts. It is not necessary that they be any tighter than necessary to keep the board from moving around.
Step 11: Install the CPU
The ESP-01 chip installs as shown with it’s antenna pointing upwards off the top of the board. The orientation matters here too. Installing it pointing downwards will damage the CPU. This gives it better WiFi reception range than if it was hovering over the other components.
Verify that you’ve got the pins lined up side to side and front to back. It is easy to accidentally install the chip with one row of pins hanging over the left or right side.
Step 12: Close The Case and Power Up!
After putting the top on the case and making sure the plate at the top is properly in it’s tracks use the 2 included longer black screws to close the case. Again avoid over tightening them. You’re now ready to power up the sensor! Replace the barrel jack from your power supply. The LED should do a “breath” cycle of fading in and out to show that the firmware is loaded and running. Since it does not know your WiFi network yet it will then go into setup mode. The LED will flash 2 seconds and and 2 seconds off to indicate that it is ready for you to connect and configure it. See the previous instruction page for the setup and usage guide.