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Archive for April, 2015


WeatherMate – Arduino Style

When you’re an avid golfer, weather tends to play an important part in trying to book advance tee times. I’ve found that in shoulder seasons, 10 day forecasts tend to be sprinkled with pixie dust. On many occasions that pixie dust turns to something you really don’t want to be out playing golf in.

The first task was to find someplace to pull weather from. This lead me to a service called Wunderground. This service pulls weather data from “PWS”, personal weather stations, all over the world via the internet.

Documentation and how it works is a little scant but the drift is this. You can sign up for a free “ID key” and with that key you can send an HTTP request and receive weather data for just about any where in the world where they have stations reporting. If you want to know what stations are around, that’s a little tougher but you can use your ID KEY with a geolocate tag and Wunderground will supply the info. Sort of. Don’t get fussy, it’s pretty generic data.

With a standard query, you name the country and area and Wunderground will deliver the weather info from any one of several stations in that area. If you want weather from a specific station, you can request that as well BUT be aware that I’ve had these stop for a few hours from time to time or not respond at all. Whereas with the area report it is 100% responsive.

With a basic non-paying Wunderground account you can pull in 500 queries a day. Should more than enough and I found any more than about every 20 minutes is largely a waste. Every half hour would be perfect I think.

You can request the data as a “.json” or “.xml” file. At this point, we have the data. Now what to do with it?

Enter the Arduino.

I had many options at this point. So, start off simple. Use an ethernet board and an LCD 4 x 20 display. Theres a “.json” parser for the Arduino, probably even an XML parser someplace. I never got that far. The display on an 4×20 LCD looked pathetic. Text. Ugh.

So I grabbed a TFT. A 320×240 3.2″ from ColdTears Electronics. I already had an Arduino Mega adapter board for it.

Whoops. Snag. Darn. I’ve yet to find a way to get a TFT display and shield to work with an ethernet shield. They both use SPI and don’t play nice together. At all.

Then I remembered I had all these WIFI modules. Some ESP8266’s, HC-21’s, HLK-RM04 and USR-WIFI232-T’s. So I started with the ESP8266 and worked my way through each of them. To see which one was the most reliable and easiest to use.

To make a long story short, formatting and sending out requests and getting stuff back is a work of frustration with these modules. Everything is an “AT” command from the 80’s when Hayes modems were in vogue and if you send too fast, time out, or the phase of the moon is wrong, these are anything but reliable. When I DID get one to work for a few hours, at some point they’d lock up and require a reboot to get going again. And parsing the data was a pain in the butt. No contest.


As I was reading the docs for the HC-21 (translated from something I don’t natively speak) I noticed the phrase “transparent” in a number of places. Okay. Transparent. Maybe that’s something. After reading way too many poorly translated pages, I found that if you simply wanted to do a TCP connection with the HC-21’s, you set them up and anything you sent out serial got sent as a TCP packet and anything that showed up on the HC-21’s IP address/port got shoved right through to the UART.

No frigging around with HTTP, parsing or anything else…mmmm. Since I have a server in the office here that runs 24/7/365 I decided I’d write a Mac program for it that would pull in the data from Wunderground, parse it, and send it out to the Arduino every “x” minutes as a TCP packet.

I connected the HC-21, set it up with a web browser, then connected it to a USB to serial converter, and finally Telnet into it from another computer and read the TCP data that showed up through the UART.

I also managed to get the USR-WIFI232-T working equally well. The RM04 and ESP8266, not so much. There was even a firmware for the ESP8266 that said it turned it into a “transparent” device but what I found was that it made it an access point with transparency, not a STA (station/bridge) with transparency.

IMG 0601

That’s a DC-DC buck converter to go from 9VDC down to the 3.3 that the HC-21 uses. I tried a simple LDO 3.3V regulator but that didn’t work at all. Instead of 3.3V, I got about 2.6 out of it. So I just grabbed a buck converter to do it, but even this one needed some adjustment under load to get it to 3.3V. The HC-21 wants 200ma! Be warned.

The HC-21 basic info:

HC 21

The UART settings for the MEGA (could have set the UART faster because the MEGA has four hardware serial ports, but I didn’t). My full string I send from the Mac is 48 ASCII characters and I use strtok on the Arduino to parse that. Works quick and simple.


Note the PORT. When I send to the HC-21, it’s like since anything that goes to port 8000 goes right out the UART.

To bridge the HC-21 to one of the office routers:

HC 21 Bridge

Notice I set the Wireless Mode to “g”. Yeah, too many of these little things like to default to “b” (like the ESP8266). So this works fine.

Lastly, set the IP info up:

HC 21 IP

I set up a STATIC IP and in my router I use the MAC address of the HC-21 wifi to make darn sure it stays at that IP.

For initial testing, I left the HC-21 connected with the USB to Serial interface. I wrote the Mac application and sent the data to the HC-21 to make sure it got there. No problem. Worked like a charm.

The HC-21 has an indicator LED on board and when it flashes about once a second like a heartbeat, it’s not connected as a bridge. When in bridge mod it flashes a double blink.

As I used the HC-21, the more I liked it. But I also found some interesting stuff out about it. First off, forget using the 3.3V output from any Arduino. When the HC-21 is running it pulls upwards of 200ma, the Arduino barely puts out 60ma on that 3.3V line. The HC-21 runs WARM, not hot, but most assuredly warm.

Once programmed, from a cold boot, the HC-21 will connect to your router in under 5 seconds. With some of the other modules, it was more like “later that same afternoon”…so the HC-21 is a nice performer that way.

After verifying that the data was getting to it, it was time to start building the Weathermate remote display.

With a strip board I put on the buck converter and a level converter. I’m not 100% sure that one NEEDS a level converter with the HC-21 to a 5V Arduino for the TX and RX but I used one any way.

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Then I wrote the sketch to receive the TCP data:

IMG 0603

The icons are stored on a 1GB SD card so if I have to update them, it’s easy. Although I could have stored them as an image right on the Coldtears display (it has room on its Font IC). I use the ColdTears library and the UTFT library.

Why the ColdTears one? Simple, fonts. Cold tears puts out some good quality displays and include what they call a “Font IC” which means there’s a number of fonts in the different sizes installed in a ram chip on the display. Rather than an external font or one that you have to add in to your upload, it’s built in. In sufficient sizes that Ive rarely had to use any of the TFT external fonts.

For a project case, I used a 4x4x6 plexiglas box that was meant for a LED matrix display. I mount the display in a piece of 1/4″ foam board so I don’t have to cut holes in the plexiglas.

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A printed graphic on the foam board gives a nice effect:

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The image itself is from my home golf course here. NorthView Golf & Country Golf Course, Canal course, #17. Depending on the wind, it can be an intimidating shot. By year end there’s enough balls in that pond that you can almost walk across it and not get your feet wet…


Spitfire – Arduino

A friend dropped off a poster that is mounted on 1/2″ MDF. The poster size was 42″ x 24″ so it’s fairly large.

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Apparently at some point in time he had someone drill some holes in the picture in strategic spots and install some grain of wheat bulbs and some LEDs. The problem was the job was never finished and he’d lost touch with the person who started the job.

Taking over with someone else’s project isn’t something that I normally do but in this case, all he wanted was some LEDs and a little flash. Right up my alley of course. So I took on the job.

First thing was to flip the board over and try to figure out what was left to do.

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Obviously there was a sale on hot melt glue for the project and after checking it out, I found none of the connections were soldered, just wrapped and the connections were corroded. To the point some of the bulbs and LEDs worked. I think I stared at the job for a while and decided it was just as easy to strip it and start over.

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The next job was installing all the LED’s, red, green, orange, white, where the old holes were drilled. I didn’t want to drill any new holes and as I worked I put in 18 LEDs.

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I used a little heavier gauge wire than the original wire wrap that was used. And of course, I HAD to use the handyman special, duct tape, to hold the parts in place. No way I was going to hot melt glue it. In the event he didn’t like it or wanted something changed duct tape was a lot easier to remove than glue.

The next choice was how to make the LEDs work. Sure I could have just wired them to a wall wart and had them come on, but I know my friend likes flashy lights so…I thought an Arduino could be pressed into service here.

Of course the stumbling block was that the Arduino doesn’t have that many outputs (18), nor does it have that many PWM outputs so brightness control was going to be awkward. Which of course made me break out the manuals to look for IC LED driver chips. Which eventually led me to the TLC5940 from TI. A nice chip, runs off 5V, has 16 PWM outputs and after a quick search, you know, someone already wrote an Arduino library for it.

I have some double sided perf boards and I thought of those first and then I spotted the single sided strip boards I have here. Oh yes, those made things much easier. I built the LED driver on a strip board.

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Inputs on one side, the 16 outputs on the other side. Back side of the board I cut the strip between the IC pins and soldered in the parts.

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I used a 10 turn pot for the current adjustment. About 1K8 would give 30ma through the LED’s but I set the pot for 2K8 to reduce that to about 12ma. There’s a formula for the resistor you can find on the data sheet. The LEDs I have are fairly high candle output so even at the “reduced” current, they are plenty bright.

Next I built up a test bed to see what I could control and how fast I could control it…and as it turned out, good thing I did.

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The library for the Arduino works nicely, and you simply make all the changes you want to the LEDs (you control EACH one with PWM) and them you send a “tlc.update()” to make the changes work. What I found was that if I tried to update too soon after setting the various outputs, nothing would happen. I needed to add a “delay(1)” before some of the update commands to make it work. No big deal but worth noting if you’re having some issue with nothing changing.

For the Arduino end, using a MINI Pro was the choice. Small, 5V, reasonably inexpensive. I’d also decided to incorporate multiple modes of display for the LEDs. A static, animated, and navigation LED’s (strobe) only. But how to control that when everything was hanging on the poster back and it’s on the wall. RF was the obvious answer.

I had a small RF key fob remote left over from another project so I added an RF receiver to the MINI Pro. I used the RC Switch library and it worked perfectly. I thought it might interfere with animation but it didn’t. Bonus.

IMG 0592

For wiring between the TLC5940 and the LED’s, I used a standard computer ribbon cable. Worked out perfect.

The first time I fired it up with all the LED’s on the poster I swear it almost lasered my retinas out. Bright doesn’t begin to describe it. Which is the point I was patting myself on the back for using a PWM LED driver IC. I added an array for the 16 LEDs that I could store their maximum brightness in. I could make all of them roughly the same intensity. This worked out better than I had hoped as well.

So how does the finished project look? Well, when my friend seen it he was in awe. When he asked if I could speed up the rate of cannon fire (it’s animated) he was surprised that I could do that with a sketch change in a matter of seconds. When he left with it, he was off to protect the skies like Snoopy & The Red Baron…


Acurite – 00592TX

Lots of Arduino ideas start off with a simple enough goal. Essentially you want to accomplish “X”. What ever “X” is.

So you start with Google to see if someone has already done any ground work to save you some time and, inevitably, frustration.

As an avid golfer, weather plays a very important part in getting out to play. When I was a working stiff like most others, on days off, if you wanted to play, you went. Rain or shine, did’t matter. There was only so many hours you had to work with.

In retirement now I’ve got a lot more fuzzy about the weather. Cold is not so critical but rain, hail, and exceptionally high winds are. You know those weather conditions where you ask yourself, “What am I doing out here?”. And you usually don’t have a logical answer?

The weather stations I have at the Wanch here work good for todays weather. So does walking to the window and looking outside. So future weather starts to play a very important part. I have a couple of Acurite weather stations that “predict” tomorrows weather because on some “magical” formula laden with pixie dust.

And thats how it all started… innocent enough.

Searching around indicated that most of these companies don’t publish their protocols so you have to reverse engineer the data stream with a probe and some software (Audacity seems to be the software of choice). Fortunately all the RF seems to center on the 433MHz band. There are scads of those things for the Arduino.

During my searching I happened across this web site:

Low and behold Brad had decoded the stream and even writing a sketch for the Arduino UNO to show how it was done. He wrote a three part series in a clear and concise manner on this so if you have the same TX unit, read all three. Worth it!

As fate would have it, I have the same 00592TX that Brad used but my base station was a little more involved than the one that Brad used. I have a 1097B station remotely connected to mine.

I decided that for clarity, I’d use a ColdTears TFT 3.2″ display (320×240). My thought was that I could use the fonts and icons that are in the FONT IC that’s included with the ColdTears displays to make some of the graphics programming easier. And to that end, it does work nice.

There are many TFT displays out there and I have many different ones here as well. From 1.8″ to 5″. Plainly stated if I want a premium display I use one of Coldtears products (they have matching shields). Keep in mind that you won’t be using one of these large TFT displays on an UNO. Mine all run on MEGA’s (2560).

So after a few false starts and problems, I got it working:

IMG 0570

I know…AcuWrong…well, when you have enough software errors cause you shouldn’t be coding when you’re tired, projects tend to take on a name of their own…

The two icons are from the IC that ColdTears has on the displays. Easy to use. The battery in the remote and the “signal strength” are shown. The battery is sent in the data stream from the remote so you can decode it and display the amount of battery remaining.

The signal strength had me going for a while. On my base station there is a four bar signal strength graph and I found that it’s not signal strength in the RSSI mode. The TX sends out four packets that are identical. The receiver then calculates the checksum on each packet and display how many packets were correct.

Some how that equates to signal strength. I guess.

I could read four packets but because of the way the interrupts work, when the signal dropped off, and I’d receive less packets I couldn’t accurately detect it. So I gave up trying.

A real time clock (DS3231) was added because I had the idea that I’d show the high and low info for the day. If you try to use my sketch you’ll probably find that there is no DayOfTheWeek2 in your RTCLib like mine. Here is my library:


The Arduino sketch for the 3.2″ TFT display. After working on this for a few days I started to realize that I really need to know what the weather will be in 2 or 3 days from today. So while this works, I think I’m going to see what I can do with API/wunderground and some XML.

Just sayin’