My reverse geocache with nixie tubes

Well, from a fellow Geocacher (Yes, this is also my GC handle) I think it's cool! I can see something like this, if the actual cache was located on the grounds of an old Nike missile site. (yet another one of my many odd hobbies).. Yes, the terrorist have put a major dent in the hobby, but it still has its fun times.. How long does the whole thing run for, seeing only a 6V supply (or is that 4.8, Rechargable?) being boosted to 180V for the nixie tubes, must be brutal on batteries!

@gelfling6- I think you'll find there are plenty of geocachers on this forum, in fact GPS is one thing that helped me to get in to arduino... Also, a nixie tube only requires about 2mA at 170V. Assuming that he's only firing one tube at a time, that's just 340mW. Even if his driver is awfully inefficient, the draw is still probably under half a watt. Nixie tubes are actually surprisingly efficient IMO, considering the amount of light they put out.

I will be darned to see terrorists use arduino-contrlled bombs on the news one day.Maybe someone's code will even be used against their good intention.

Well they better be selective on whos code from this forum they copy. If they use any of mine, there will most likely be a few less terrorists to worry about. ;D

Lefty

Very cool project... inspired me to get started on a nixie clock a few days ago. I gotta tell ya', making these things from scratch is a real challenge... After scouring over online schematics I just ordered a ton of MOSFETS, schottkys, inductors, HV caps, 25 MPSA42s, etc. from digikey only to realize that to multiplex tubes I also need HV PNP transistors. :o I'm also using way too many transistors, right now with my current schematic for only four tubes I'm at all 25 MPSA42s, 4 MPSA92s (anode switching), 14 general purpose switching transistors, and total of 13 IC pins just to switch the tubes (not including the pins of the ATTiny45 controlling the high voltage PSU).

Kudos to you for making a very clean, non-parts-intensive build (albeit with the help of some control ICs :P).

I don't do any multiplexing, so I'm just using 3 anode resistors, 4 155id1 (= russian version of the SN74141) and 3 4017 binary counters. I drive them directly, because the tubes are brighter this way and I actually need less power because the firing of the tubes is pretty expensive power-wise.

I need the extra 155id1 for the decimal point on two tubes that is driven separately from the digits. I just need two outputs from that driver so I get along with two inputs. Switching on the digit one from this driver lights a decimal point before the second digit and the two is a decimal point in front of the third digit. I also could've wired the point on the first nixie, but I decided that something like .845 would look weird and 0.85 is precise enough for this application.

I also used a prebuilt power supply to get the 180 Volts (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140426808956) once I realized that you have to be very careful on placing the components on the converter to get an efficiency over 80%.

I can highly recommend this, it's not much more expansive than buying the components (Unless you order the MAX1771 that you need as a sample), it's tiny, works perfectly and can be switched off completely via the arduino.

Some comments on power:

With all three tubes lit the circuit draws 500mA and under 100mA without them. The tubes light for about 10 seconds per distance fix and it needs about 60 seconds to get the fix. So there's an average power consumption of 200mA.

The batteries (NiMH D-cells ) have 6000mAH but because of the voltage drop I'm just counting them in for 3000mAh.

That should be enough for 15hours continuous operation, or at 90 seconds per fix, 600 fixes which is enough to find the target coordinates.

[edit] PS: This is where I got the tubes and driver ICs from: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250749058503, they also come with nice pins that you can solder to a board to make your own socket.

In case the auction is gone when you read this - this is the seller: http://shop.ebay.com/buyer.md/m.html . The tubes are called IN-12b. [/edit]

As there seem to be some geocachers here - I have another idea for an arduino-powered traditional geocache.

I’d love to do this myself, but since I’m in the middle of a big city I can’t find the right spot to pull this off anywhere near me where I could maintain it.

Here’s the idea:

You make a plastic cache-container that can close with a servo from the inside like my reverse geocache. You’ll add an arduino, some kind of display mounted in the lid and an rfid reader with the antenna on the bottom of the container. For power supply I’d add a 9V battery holder that can be accessed from the outside.

Then you hide the cachebox in a place from where you can see two distinct landmarks (a bench, some kind of tree stump, etc.). In the cache listing you’ll tell the people to bring a 9V battery.

When the cacher finds the cache it won’t open. They insert the 9V battery and the display says ‘put me on the red mark on the bench behind you’.

There’s an rfid card glued under that spot and when the cacher puts the box there the reader sees the rfid and the display says 'Put me on the treestump 200 meters north of here - you have 50 seconds… '. A countdown from 50 begins.

If the cacher does’t put the box on the rfid chip in the tree stump within the 50 seconds he has to start over (put it on the bench). If he makes it the box says ‘Now back to the bench, you got 45 seconds’ :slight_smile: and the countdown starts.

If he makes it back to the bench in time the box opens. To close it again he has to take out the battery and put it in again or put the box on a third rfid chip.

Would be real fun if you would install that somewhere where you could watch the people running around :slight_smile:

You could also add more rfid stations or make them run faster.

[edit]
If you find a spot where there’s something like a grid with different field on the ground (like these giant chess boards in parks) you could also make out a kind of puzzle where you have to place the box on different fields with rfids buried in them due to hints on the display. Like just displaying ‘A3-D5-F3’ with the chess board.
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Wow that's a really great idea RickP. Something to think about, and finally something useful for my bag of RFID tags I have here ;).

BTW, great job on your project. Looks really great / professional :).

I will be darned to see terrorists use arduino-contrlled bombs on the news one day.

I don't think that's the kind of thing we get told about.

Real great idea RickP. I could also add a GPS sensor and give orders like "Jump in your car and exceed the speed limit on highway I-xx westbound for at least 30 seconds, near the bridge where cops normally hide" ;D

Maybe a safer way is to add a few tilt sensors and give an order to flip the box so that it would open just like pressing a few keys on the keypad in the right sequence, maybe safer this way ::)

By the way, I just registered on geocaching not long age and I'm waiting for snow to melt in a few months so I can go on a few advantures with my wife. I will definitely design a flip-2-open box once I get a hang of the geocaching.

Hey, thanks for the advice on the power supply. I got mine built and I'm only seeing around 60% efficiency when boosting from 5v to 170v (5v 170mA in, 170v 3mA out). I'm going to rejigger the circuit so that using 9v won't fry the attiny and see what happens then. It also seems that I can't get more than 130 volts with a 28000 ohm load, but this may be due to me capping the duty cycle at 98% (the attiny automatically adjusts duty cycle so the output is 170v). I'll work on it later today.

Edit: GAHHHHH. I feel like screaming. I've spent the past five hours wondering why the #^%$ my boost circuit was only putting out ~70V after I tried to get it to work with 9V in. I proceeded to completely disassemble my perfectly soldered and very small boost circuit in order to exhaustively test every single component-of course, the component that had failed was the VERY last one I tested, and I only even tested it as an after thought. It was the output filter capacitor. There was no reason that thing should have failed, it was way over the required voltage rating. So now I have to re-assemble everything, and I'm out a really big filter cap. I almost trashed my inductor.

To anyone considering building a nixie clock, I HIGHLY recommend not building your own power supply, LOL.

On the plus side, it now works perfectly and holds stable at 9mA draw (set to regulate at 170v).

Now it's all over the net:

Make magazine: http://blog.makezine.com/archive/2011/01/nixie_tube_reverse_geocache_box.html

Gizmodo: http://gizmodo.com/5728632/this-clever-diy-briefcase-only-opens-when-youre-at-the-right-gps-coordinates

and various other sites. It's kind of cool, but I really hope the guy who this box is for (his birthday is in 4 days) doesn't stumble over it :-/

I saw those! Congratz on the fame, it was a very cool idea. And plus, if he does stumble over it, he probably won't connect the dots until his birthday, at which point he will be all the more enthralled.

Very awesome job there :D Great concept. Congratulations :D

This is probably one of the cooler projects I have seen.

You should release instructions or blueprints somewhere so some of us can replicate it! :D

Hi Rick. Could you please snap a picture of the correct wiring for the relay? I have a complete reverse geocache with everything fine and dandy except the switch mechanism. I've been fiddling around on the breadboard for hours and can't seem to make the arduino power itself down. The schematic you posted is helpful but I still find myself confused in the actual implementation. Thank you very much for all the info on your awesome project!

Will

Hi Rick. Could you please snap a picture of the correct wiring for the relay?

Will

I made a schematic for you - I hope that's helpful. Maybe you'll have to wire the pin 4 of the relay instead of pin 2 to the arduino 5V - I did this from memory :)

When you press the button the relay should latch and switch on the 5V for the arduino. If you put D2 to high it should switch the power off.

[edit] Forgot the image :)

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Rick, do you have any idea how much current that relay draws when it's in its quiescent (off) state? Could your box last for, say, 6 months as long as the buttons weren't pushed?

Also, you mentioned the ability to use the button as both a power switch and an input to the Arduino, but I gather the circuit you share above doesn't show the latter? If you wanted to add this, I guess you'd just connect the relay pin 1 line (from the button) to an Arduino digital input?

Thanks! This is good stuff.

Mikal

Rick, do you have any idea how much current that relay draws when it's in its quiescent (off) state? Could your box last for, say, 6 months as long as the buttons weren't pushed?

Also, you mentioned the ability to use the button as both a power switch and an input to the Arduino, but I gather the circuit you share above doesn't show the latter? If you wanted to add this, I guess you'd just connect the relay pin 1 line (from the button) to an Arduino digital input?

Thanks! This is good stuff.

Mikal

It doesn't draw any current. The latch relay is like a switch that is operated by magnetic coils. When it's off there's no connection between pin 2 and 3, so no current flows.

You can connect pin 1 to the arduino to use the pushbutton but if you do so you should add a clamping diode between pin 1 and 5 like on the other side. You need that because there is a short spike of energy with reversed polarity in a relay when you cut the power to a coil. That could damage your Atmega chip without the diode.

If you try this o a breadboard start by applying 5V to the relays coils (Pin1&5 and Pin6&10 in my schematic). You should hear the relay clicking if you put power to the alternate coils. Then check the resistance from pin 3 to pin 2 and 4 and you'll see how it works.

[edit] BTW: Thanks for the tinyGPS library! I used it in this box :) [/edit]

BTW: Thanks for the tinyGPS library! I used it in this box

Thanks! Glad it was helpful.

One last question. (I'd really like to try that relay solution.) What species diode is that that you use to clamp against polarity reversals in the TQ2SA.

Mikal

One last question. (I'd really like to try that relay solution.) What species diode is that that you use to clamp against polarity reversals in the TQ2SA.

Mikal

A 1N4148 is recommended but if you just have a 1N400x you can use that, too.