Yes, You Can Print TPU On A CR-10s With No Mods

A good friend of mine has a dad who’s suffering from dementia. He’s a farmer and spent decades building and fixing things, and he still likes tools and things he can manipulate with his hands. Unfortunately, there are times when he throws things.

I printed him up some big nuts and bolts in PLA but realized that if they were all screwed together they’d make a pretty hefty projectile. So I wasn’t entirely sure what to do. Then, I remembered there were some 30g sample packs of TPU sitting around and collecting dust, so I figured I’d see if I could do something with them.

Having never printed TPU before, it was a few hours worth of DuckDuckGoing (I know it doesn’t roll off the tongue as well) before I’d learned that yes, it was possible to print TPU on a CR-10. I’d also learned that no, it wasn’t possible to print TPU on a CR-10. Interestingly, it was also possible to print TPU on a CR-1o, but only if you installed anywhere from $0.50 to $250 worth of modifications.

I opened one of the packages and played with the filament. Rubbery, stretchy, a little squishy… definitely different from the PLA and PETG I’m used to. So, I loaded it into the printer, started a print, and sat there for the entire thing so I could dial the settings in while it printed (thank you Octoprint!!!).

Here’s a bendy wrench:

TPU wrench
Before [model by triffid_hunter , see https://www.thingiverse.com/thing:11647]
TPU wrench
Bendy!
TPU wrench
… and it springs back on its own

I then fused what was left of one pack with the other pack I had (and set off the smoke alarm, whoops). After things calmed down, I drew up and printed a nut and bolt, which came out really well:

TPU nut and bolt
TPU nut and bolt

I did this on my CR-10s with a 0.4mm nozzle and no modifications, and the TPU I used had the following recommendations listed on the pack:

  • Colour: Black
  • Material: TPU
  • Dia: 1.75mm
  • Nozzle: 220C-240C
  • Bed: 75C-85C

After a bit of experimentation, here’s what I found worked for me. Again, this is on a stock CR-10s with a 0.4mm nozzle:

  • Level your print bed. Actually, go level it now even if you’re not going to print TPU. It fixes sooo many problems.
  • Clean the outside of the nozzle before you print.
  • Purge whatever was in there before. Do not mix TPU with another material, even if it’s “just a bit”. Trust me.
  • Bed surface: Glass with two layers of Elmer’s all-purpose glue stick, applied after the bed is at temperature.
  • Bed temperature: 75C (all layers).
  • Nozzle temperature: 240C (all layers).
  • Fan: 0% for first layer, 100% for rest of print.
  • Flow rate: 105% (all layers).
  • Retraction OFF.
  • Print speed: 18-21mm/s.
  • Layer height: 0.2mm for first layer, 0.25mm for rest of print.
  • Print with a skirt, at least 7-10 lines wide.
  • After the hotend and bed are heated up and just before you’re ready to print, raise the hotend 100-150mm and wait until the nozzle stops drooling TPU. Clean up the debris, carefully wipe the excess TPU from the nozzle, then start the print. It will take a while for the hotend to fill up again – print with a skirt to give it time to fill back up (see above point).

With these settings on this printer and with that particular flavour of TPU, I was able to get good strong prints that looked pretty good. There is some stringing between parts, but it cuts away easily with a small pair of scissors or snips.

I lobbed the wrench at my wife, who reported that it didn’t hurt. I screwed the nut onto the bolt and threw it at the front door and it bounced nicely without leaving a dent. I think these might work for my friend’s dad.

I’ve ordered some more TPU, and of course I couldn’t find stuff with the same temperature recommendations as the sample packs. I will give it a shot and do up another post with what I find out. At this point, though, I’m pretty comfortable with saying that yes, you can print TPU on an unmodified CR-10s and it can turn out well. Just go slow. And level the print bed!

ESP32-Cam Antenna Workaround

A while ago I got my hands on a pair of ESP32-Cam modules. They were crazy cheap and it looked like I had a great little device that would work well as a security or wildlife cam:

It’s tiny!

It was easy to program using the Arduino IDE and the example program, but no matter what I tried changing in the program it wouldn’t connect to my home wireless network.

There’s a lot of documentation out there on the ESP32 devices, but there are parts that seem to be missing. I wish I’d bookmarked the link, but I came across the comment section of one article that mentioned a 0R surface-mount resistor that selected the external antenna jack or the on-board PCB antenna. It didn’t take too long to find, and it was set to use the external antenna jack:

That explained why it wasn’t talking to the wireless – no signal. I could fix the problem in two ways: plug in an external antenna, or move the tiny little resistor so that it connected the ESP32 to the PCB antenna. I don’t have any connector that will fit that jack, so I decided to move the resistor.

**NOTE** Doing any combination or number of the following steps will definitely, POSITIVELY void the warranty of the device. It may also increase the electrical noise produced by the unit and/or its susceptibility to other sources of electrical noise. It may also cause operational or stability problems. It may also cause the device to produce wifi signals that are more powerful than allowed by law. Proceed at your own risk.

Unfortunately, between not being able to see it very well (even with a magnifier lamp), having a soldering iron with too large a tip, and having tingly fingers and shaking hands, I ended up with this:

Not only did I not manage to solder the resistor in place, I also ruined the PCB pad that connected back to the ESP32.

By this point I was getting pretty frustrated. Actually, I don’t think I’ve been that frustrated in quite a while. Fortunately, I had another ESP32-Cam that I could apply the knowledge that I gained on this one and not make the same mistake twi-bahahahaha… yeah, I ruined that one, too.

The two of them together cost me less than $15, but I hate throwing something out when it’s still “alive” (they both still booted and tried to connect to the wifi), and I was looking forward to playing around with them. Seeing as how they were pretty much garbage at this point anyway, I figured I’d see if there was anything I could do to get them working.

**NOTE** See previous note. Seriously.

I could see the PCB trace leading under the metal can, so I figured that if I was careful, I might be able to remove the can and find another soldering point to attach an antenna.

To remove the can, you don’t need a hacksaw or a Dremel… just a pair of very fine-tipped pliers or snippers. there is a small hole in the can in the inside corner right by where the antenna selection resistor pads are. Carefully grab it with the pliers/snips and pull straight upwards to make some room:

Slide the pliers in a bit more and lift up and away from the PCB antenna (towards the top of this picture). It may take a bit but the can end by the PCB antenna should break away:

Reposition and pull the can up and to the left – the right side and top should come free easily as well:

Reposition again and the last bit should break away with very little force:

The antenna connection point is – very nicely – right by where the antenna selection pads are, right between two surface-mount components with big pads and lots of solder:

So now to make the antenna. I used a piece of 26ga solid wire-wrap wire, but anything nice and thin will do 22ga is too big.

Cut a piece about 6.5cm long, then strip about 1-1.5mm and bend the stripped part at a right angle. Tin the wire, make sure it’s got a good coat of solder on it:

Bend the insulated part of the wire to whatever shape and angle helps you hold the stripped part in place at the new attachment point. Use the iron sparingly – if you’re heating and heating and it doesn’t seem to be melting, back off, give it a minute, and change your angle before trying again.

If you’re careful and lucky, you’ll end up with something like (or much better than) this:

Gently bend the antenna into the orientation you prefer, and you’re done!

Reminds me of one of those facehuggers from Alien

The next thing to try is powering it up (unless you haven’t programmed it, in which case you should probably do that now). With no can and a crappy detuned wire antenna, the ESP32-Cam was able to finally connect to my home wireless network:

FINALLY

And the camera’s video streaming works like a charm:

I suppose that instead of hanging a wire antenna off that point, I could’ve run a jumper from the new attachment point to the pad that connected to the PCB antenna (or the antenna jack, for that matter), but a) I just thought of it, and b) I don’t mind the crappy antenna look.

Portable Power For The GQRX Pi 4

I’ve been enjoying finding and listening to all kinds of stuff with the SDR, and since I got it working with the Pi 4 I’ve wanted to use it without needing an extension cord.

I had a lot of trouble finding a battery supply that would do the trick. I have a few of those USB power packs at home and tried them but the Pi kept reporting low voltage.

I then turned to putting a regulator on a 12V SLA battery. Unfortunately, even with capacitors and shielding, the switching regulator I tried put out a lot of noise that the SDR picked up. I knew a linear regulator would be quieter but as I suspected, it only took about a minute before the biggest heatsink I had was too hot to touch.

So… I went back to the USB battery packs.

There are a few problems with those packs. They can also be noisy (there’s switching circuitry in them too), they can sag under load, and most of the USB cables out there are cheap crap that use very thin wire.

I put a load (actually, a Pi 2) on each pack and watched what happened to the noise and voltage on the oscilloscope. The best of the lot turned out to be an older Anker Astro E4 13000mAh unit that held a pretty constant 4.92V and wasn’t too noisy. So I started there.

I don’t know how many USB cables (or pieces of USB cables) I have sitting around. Some came with phones, tablets, or other devices… some were bought separately… some looked good… some looked cheap. I started going through the cables to see what kind of voltage drop there was when there was a Pi 4 on the end (with a micro-USB to USB-C adapter).

None of them ran the Pi without triggering the low voltage warning, and some of them couldn’t run the Pi without triggering the voltage warning even when idle. Two of them were so bad that the Pi couldn’t finish booting. The voltage drop across the cables was as much as 0.62V!

With those results, I decided to make my own cable. Unfortunately, when I looked in my USB parts drawer, I only had micro-USB plugs and USB type A jacks.

Out came the snips and I started chopping up the cables, starting with the ones that looked the best. Turns out that how a cable looks doesn’t mean much when it comes to how heavy the wire inside it is.

Eventually I found one that had considerably heavier wire than what I’d seen up to that point, so I decided to use it instead of chopping up the rest of the cables. I cut it to 60cm, soldered on the plug end, and gave it a try.

It was a lot better, but the Pi was still reporting that there’d been a low voltage condition at some point. I cut the cable to 50cm.

Then 40cm.

Then 30cm.

Then 20cm.

20cm did the trick, and I couldn’t trigger the low voltage warning anymore, even with the SDR plugged in and running and the CPU pinned to 100% (I usually use cat /dev/urandom > gzip > /dev/null for that).

Here it is, the beautiful and reliable USB cable of portable GQRXing:

Yeah, that’s hot glue. Works well and it’s strong but doesn’t look all that great…

Since I only had the micro-USB plugs on hand, I still have to use the adapter, which could also be wasting a bit of power. I need to order some other stuff sometime soon so I may grab a couple of parts to make another good cable or two.

To test the cable and battery pack, I hooked it up to my SDR Pi, fired up GQRX, told it to record the audio, and checked in on it every half hour. It ran for six hours before the battery LEDs showed it was at less than 25% capacity. I don’t like running those packs flat so I stopped the test there.

Before I shut down the Pi, I hopped onto it (using VNC on my phone, heh) and checked whether any of the warning conditions had been triggered (voltage, temperature, etc). Here’s what I saw:

0x0, or no problems at all… after running for six hours straight. Not too shabby!

This Is Why They Talk About Drying Your Filament

I went to start up a print today and loaded an old half-full spool of black PETG into the printer. I ran the filament through the nozzle to purge what was left of the previous filament and, as the white plastic faded to grey and then black, I heard an odd ticking sound coming from the nozzle.

I store my filament in zipper bags with a pack or two of desiccant, but even with those precautions, it only slows moisture down – it doesn’t stop it. It’ll make its way in through any tiny hole in the plastic, and water molecules can slowly make their way between the molecules of the plastic bag. You can’t see it or feel, it but with enough time and the right conditions, it’s enough to saturate the desiccant and start working its way into the filament.

In this case, the bag containing the filament spool had been sitting long enough and had gone through enough temperature/moisture cycles (I store it in the basement) that the filament had absorbed some moisture. The moisture was evaporating and creating bubbles and little pops in the plastic as it went through the nozzle at about 220° Celsius:

Bubbled Filament
You can easily see and feel the bubbles even though the diameter of the filament is only 1.75mm.

If I really wanted to, I could probably still print with it, but the printed surface will probably be rough and adhesion wouldn’t be as good.

Fortunately, drying filament is pretty simple. Machines dedicated to drying filament are available, and while they have trays and covers made to fit filament spools, I found them to be a bit too expensive for my budget. I ended up buying a cheap food dehydrator from my local hardware store and drilling a couple of holes in an old Tupperware container to use as a lid:

Now I just need to let it sit for a while and the filament will be good to go!

GQRX On The Raspberry Pi 4

I’ve been playing with SDRs on the Raspberry Pi 4 for almost a month now and I am happy to say that the new Pi (at least the 2GB model) has enough oomph to run GQRX with a Great Scott Gadgets HackRF One (at 4MSPS max), and a NooElec NESDR SMArt. I was SO happy to say it, I spent several hours writing up a howto, just for everything to fall apart at the second last step.

So… here’s a short version. If I get enough questions about it, I’ll look at salvaging what I still have and writing it up in detail again.

To get GQRX working on the Raspberry Pi 4B (the 2GB is the only version I have), you will need the following:

  • A Raspberry Pi 4B (I only tested with the 2GB version but I expect it will work fine with both the 1GB and 4GB versions)
  • An 8GB Class 10 (or larger/faster) microSD card
  • Internet connectivity through a wired Ethernet port
  • An Ethernet cable
  • An SDR (tested with the HackRF One and the NESDR SMArt)
  • An antenna that fits your SDR
  • A USB cable that fits your SDR (if necessary)
  • Headphones or a set of speakers with a 3.5mm plug
  • A heatsink and/or fan for the Pi (it requires so little cooling that you can just point a desk fan in its general direction and it should be okay)

So, here’s how to do it:

  • Image the microSD card with the official Raspbian version with desktop but without the extra software. Get it from here.
    Get this version of Raspbian
  • Connect it to an Ethernet port and power it up, then find it on your network and do the usual password/configuration/update steps.
  • Set the resolution to 800×600.
  • Force the audio output to the headphone jack.
  • Enable VNC.
  • Install GQRX from the respository (sudo apt install gqrx-sdr).
  • Connect to the Pi via VNC and turn the system volume down.
  • Connect your SDR (with antenna)
  • Run GQRX. If you’re having trouble or for information on settings, etc, check here for information.
  • In the “FFT” tab, change the
  • Turn up the system volume and/or software or hardware amplifiers in GQRX and your SDR until you can comfortably hear a signal.

And that’s about it.

I found, though, that I wanted to make the Pi a little more portable, and when using the Ethernet jack there seems to be a bit more noise in the GQRX display. Here’s what I did:

  • Install RaspAP, information and installation instructions are here.
  • Set up the Pi to be a wireless access point on a separate network from your Ethernet port.
  • Once the AP is running, disconnect the Pi from the Ethernet port and, using your computer, phone, or tablet, look for the SSID of the AP you set up and connect to it.
  • Once connected, run a VNC client (I use VNC Viewer by RealVNC but others should work as well).
  • I lowered the output power of the Pi’s wifi transmitter because I wanted to save as much power as possible, lower the amount of electrical noise the Pi generated, and keep the AP’s range as small as possible so as few people as possible can see it. To do that, add the following line to /etc/rc.local just before the “exit 0” line:
    iwconfig wlan0 txpower 5
    Change the value for txpower to whatever suits your needs (lower = lower transmitter power).
  • If you find you can’t connect to the AP or you want to change or update the Pi, you can always plug it back into the Ethernet port and connect to it that way.

Here’s what you’ll end up with (except with sound – my PC’s microphone isn’t working):

You can also ignore that last block of instructions and just hook the Pi up to an internal or HDMI-attached display. Some people find that using displays with resolutions of 800×600 or less cramps the GQRX display and makes navigation difficult. If you’re running VNC, you can set the resolution to whatever you want – just keep in mind that the Pi will start to sweat and lag if the display is too large.

If the Pi seems to be having trouble keeping up, try the following:

  • Make sure your Pi is adequately cooled and powered. Run vcgencmd get_throttled and if it shows any number other than 0x0, you have a temperature/power problem.
  • As mentioned above, lower the display resolution.
  • Remove the Raspbian desktop picture and replace it with a single colour.
  • In GQRX, one of the biggest CPU hogs is the main display. Go into the “FFT Settings” tab and lower the FFT Size and Rate. I use 8192 and 10fps on my Pi and that seems to work reasonably well.
  • Once you find the frequency you want to listen to, minimize GQRX. That should speed things up noticeably.
  • Lower GQRX’s sample rate by going into the “Configure I/O Devices” window (the little green PCI card icon) and lower the number. The HackRF in particular needs to be set lower than its 10MSPS default. 3-4MSPS for the HackRF and 2-3MSPS for the NESDR SMArt seems to do the trick.
  • Don’t run any extra services or applications on your Pi.
  • If you’re recording audio and it’s lagging or chirping, don’t record to the SD card – mount external USB storage (stick, drive, whatever) and use that instead.

The Pi – even the 4B – has its limitations. If you’re careful, though, you can pretty easily turn it into a small, portable, and powerful little SDR machine.

Software Defined Radio

On one of her visits a little while ago, Ms Geek brought over a box full of her hobby stuff for me to try if I was interested. One of the things in the box was a HackRF One Software Defined Radio (SDR). I had no idea devices like this existed, and we downloaded some software and she showed me how it worked. It’s… well, it’s a radio receiver (the HackRF One can also transmit!) that you connect to a computer by USB. If you’ve got the right software, the right drivers, and the right antenna, you can browse a good chunk of the radio spectrum and listen in to all kinds of neat stuff.

I tinkered with the HackRF for a while but didn’t have a lot of luck. One day, I found some old cable, soldered some BNC ends to it, and put the antenna outside.

What a difference – the whole thing came to life and I could hear (and thanks to the software, see) all kinds of stuff! Conversations between aircraft and the tower at the airport, weather reports, radio stations, what was wrong with city buses… all kinds of fascinating things.

Here’s the HackRF One, it’s roughly smartphone sized:

Not a great picture, it’s dark in here…

And what a neat machine it is! Radio and antennas are two things I know very little about, and while there’s a learning curve, it didn’t take too long before I was able to tell the difference between voice and data signals and use some of the software settings.

I figured that Ms Geek would probably want her SDR back at some point, so I figured I’d look into picking up one of my own. While the HackRF One is a really nice device, it cost more than what I’d hoped to spend, particularly since this is a brand new hobby.

Enter the NESDR SMArt:

Yep, still dark…

I found a bundle online for about 35 bucks that included the SDR, three antennas, and a magnetic antenna mount. The NESDR is a lot smaller than the HackRF One but it can’t listen to as much of the spectrum and can’t transmit. That’s okay though – I’m still just barely scratching the surface what what these devices can do.

I’ve been spending a lot of time browsing the airwaves and listening to various services or systems and trying to figure out what they are. Some are pretty easy, like the airport. They announce who they are with every transmission. Others, though, aren’t quite as easy to figure out, like who was whistling and then asking about a trailer of dirt, or where “home one” is. Then, there’s stuff like this:

What the hell is that? It whistles and every once in a while it changes pitch and frequency like in the picture. I have no idea what it is but I’m fascinated.

I’ve been playing with the SDR stuff every day since I moved that antenna outside, and every day I find something new and different. What a neat hobby!

It’s Here!

My order of Raspberry Pi 4s and a couple of doodads for them arrived today!

Had a bit of trouble with VNC, need to specifically enable it in raspi-config and change the resolution from the default, also in raspi-config (I’m using 1280×720). Since then, things have been going well. This board is FAST!

World’s Crappiest Oscilloscope… v1

When Ms Geek gave me an Arduino Leonardo to play with, one of the first things I did was go through the examples. After almost two decades of experience with PICs, I was amazed at how easy it was to get things like serial communication and ADC working. Don’t get me wrong – I’m still a PIC guy… but I think I’m an Arduino guy now, too.

The ReadAnalogVoltage example caught my attention because it was so simple. Here’s the setup. It’s just a potentiometer with one end terminal connected to +5v and one to GND, and the wiper connected to A0:

Not much to it, eh? That bent yellow wire in the middle just holds the Leonardo in place.

I played around with it for a while and watched the output on the Serial Plotter, but then I had a thought. You need to run the Arduino software to use the Serial Plotter, and besides, the Serial Plotter looks too nice. Half-remembered days of coaxing dusty old VT100 and TN3270 terminals back to life and running a BBS made me think – I could do the same thing, but not as good!

I dug through some of my old PIC programs and found a serial terminal that I wrote back in 2002. Between that and the ANSI sequences at http://ascii-table.com/ansi-escape-sequences.php, I stapled together a really bad looking display that I like to call the World’s Crappiest Oscilloscope, v1. Here’s the program:

// World's crappiest oscilloscope v1
// Borrows heavily from ReadAnalogVoltage example in the Arduino Examples menu
// Uses Arduino Leonardo, reads voltage on analog pin A0, then uses good old ANSI
// codes to
// draw a really bad oscilloscope in a serial terminal.
// A little amusing but very useless.
// Info about ANSI codes is at http://ascii-table.com/ansi-escape-sequences.php
// **THIS PROGRAM IS FREE TO USE AND MODIFY AS YOU SEE FIT**

void setup() {

  pinMode(A0, INPUT); // Set pin A0 to input.

  Serial.begin(9600); // initialize serial communication at 9600 bits per second.

  delay(3000);  // Should be enough time to start up a serial terminal.

  // Warm up the tubes...
  Serial.write(27); // Clear terminal screen with ESC [2J and ESC is ASCII 27
  Serial.print("[2J");
  Serial.println("Warming up the tubes, please wait...");
  delay(2000);  // This just here for dramatic effect.
  Serial.println("Starting...");
  delay(2000);  // This also just here for dramatic effect.
}


void loop() {

  // Now set up the fancy oscilloscope screen. Ah, the good old ANSI days...

  // Set Oscilloscope screen to white markers on black background.
  Serial.write(27);
  Serial.print("[0;37;40m");
  
  Serial.write(27);  // Clear Terminal screen with (esc)[2J, (esc) is ASCII 27
                    // Serial.write sends binary data to the serial port
  Serial.print("[2J");
  Serial.write(27); // ESC again.
  Serial.print("[H"); // cursor to home.

  // The following lines draw the scale up the left side of the terminal screen and
  // the bottom border.
  Serial.print("5.00V|\r\n");
  Serial.print("4.75V|\r\n");
  Serial.print("4.50V|\r\n");
  Serial.print("4.25V|\r\n");
  Serial.print("4.00V|\r\n");
  Serial.print("3.75V|\r\n");
  Serial.print("3.50V|\r\n");
  Serial.print("3.25V|\r\n");
  Serial.print("3.00V|\r\n");
  Serial.print("2.75V|\r\n");
  Serial.print("2.50V|\r\n");
  Serial.print("2.25V|\r\n");
  Serial.print("2.0V0|\r\n");
  Serial.print("1.75V|\r\n");
  Serial.print("1.50V|\r\n");
  Serial.print("1.25V|\r\n");
  Serial.print("1.00V|\r\n");
  Serial.print("0.75V|\r\n");
  Serial.print("0.50V|\r\n");
  Serial.print("0.25V|\r\n");
  Serial.print("0.00V|________________________________________________________________________________\r\n"); // 80x _
  Serial.print("                         WORLD'S CRAPPIEST OSCILLOSCOPE v1\r\n");

  byte ColumnCount = 7; // Okay, there are 50 columns to put data into, starting at column 7 and ending at 57.

  while (ColumnCount <= 87){
    int sensorValue = analogRead(A0); // read the input on analog pin 0. Need to use an int because it's a 10-bit number.
    
    float voltage = sensorValue * (5.0 / 1023.0); // Convert the reading (which goes from 0 - 1023) to a voltage (0 - 5V).

    int OscOut = (voltage * 4);  // so far so good but need to make it go the other way
 
    OscOut = 21 - OscOut;

    // now, staple everything together into one string to control the cursor
    // Control cursor position: ESC then [line;columnH
    
    String OscStr;
    OscStr = '[';
    OscStr = OscStr + OscOut;
    OscStr = OscStr + ';';
    OscStr = OscStr + ColumnCount;
    OscStr = OscStr + 'H';

    Serial.write(27);

    // Just for kicks, let's try to change the trace colour to green.
    Serial.print("[0;32;40m");

    Serial.write(27);

    Serial.print(OscStr);
    Serial.print("*");

    ColumnCount = ColumnCount +1;
  
    delay(50); // wait a bit before going back so the screen doesn't fly by too quickly.
  }

}

I really need to figure out how to widen the blocks in this theme… it kind of mangles the formatting. If you copy and paste it directly, it still works though. This is what it does (don’t start the video unless you have a strong heart – it’s THAT amazing):

I wonder if there actually were any of those old terminals set up with something like this back in the day…

It’s Not Lupus

I stumbled across this yesterday – it’s right out of the pilot episode of House M.D.:

Surgeons opened her skull to remove a cancer tumour – then they saw a tapeworm” – nationalpost.com, June 7 2019

Disgusting, fascinating, and ultimately good news – the victim says her symptoms have gone away “almost 100 percent”.

Remember, folks – wash your hands and cook your pigs.

Fixed The Old Weather Station

I got a nice little weather station as a gift about a decade ago. It’s been pretty accurate and the display is usually nice and bright and colourful. Over the last while, however, the backlight has gone from bright, to flickering, to flashing once in a while, to completely dead. This made the unit almost useless unless it was daytime and you were standing right in front of it.

Today I cracked it open and gave fixing it a shot. It came apart pretty easily, but I learned later that with the problem I had that I didn’t need to remove the green circuit board. Removing it led to a lot of frustration and grief as it took me many tries to get everything lined up again.

Anyway, it turned out that there were two problems. One was that one of the wires wasn’t actually soldered to the backlight – there was a glob of solder and the wire was just resting against it. I thought that’d be an easy fix but unfortunately, it didn’t make any difference.

What I ended up doing was ignoring the original LED driver circuitry altogether and connected it to the power jack (tip positive). I put a two-pin female header in series to I could easily try different resistors:

1K was a little dim, 100 ohms was better, but I finally settled on 47 ohms. That made for about 110mA, well within a regular 1/4W resistor’s capacity, and considering there are four LEDs in parallel, that’s about 28mA per LED – nice and low. I’m pretty pleased with how it’s working at this point:

Nice and bright

Still, I’m going to run it for a few days to make sure that the resistor and backlight aren’t warming up before I solder the resistor in permanently and button the whole thing back up.

Hopefully this means I’ll get at least another ten years out of it.