All - I just wanted to let you know about an archive I just released on my website, which includes articles and information on interfacing the Armatron to a computer (or a microcontroller, like the Arduino); it can be found at:

http://www.phoenixgarage.org/show_article/92

In addition - if you are looking for an Armatron to hack, I just found out that Discovery re-released it as the "Spark":

http://www.phoenixgarage.org/show_article/93

I hope that the archive will help somebody out there, or at least give them some inspiration!

 

I was thinking of a small IR/LDR based intruder alarm (kids will have fun putting it up in their rooms) any other such suggestions which kids can relate to and apply in their own worlds?

This reminds me of a project back when I was in grade school (5th grade); my friends and I were constantly missing things (pencils and paper, mainly) from our desks (assigned seating, old-school lidded desks), we suspected the teacher.

I ended up rigging an alarm using my 150-in-one kit from Radio Shack and a custom trip-wire like switch to the desk lid; it could be turned off if you knew what to do by carefully openning the desk, reaching in, turning it off with another switch.

Imagine our surprise when, during recess (do kids even get recess anymore?), the alarm sounded very loudly and our teacher ran out calling my name to come shut the thing off. I turned it off, looked at her, then went back out to recess. No other words were exchanged that I remember.

I was never sent to the principal.

Our desks were not messed with the rest of the year.

 

If you only use low capacity batteries they will just get warm and not explode when the polarity is reversed.

I've never intentionally tried it, but couldn't they potentially vent and leak (I don't consider venting to be the same as exploding, although exploding is the same as venting - just in a violent and quick manner!)?

I'll probably get flamed for this, but...

I assume that these kids have already been introduced to the history of electronics, and have knowledge of the Leyden jar, correct? Perhaps they have even constructed one? Because otherwise, they will be getting an incomplete education on electronics.

Giving them a capacitor, showing that it can be charged up and discharged does nothing more than show them another "magic black box", the same as likely how they view their computer, their television, their cell phone, the family automobile - indeed, a myriad of devices that they (and most likely their parents) have no concept of the history behind, the people involved, the trials those people went through to develop it; in short, how it all really works in the end, and most importantly, why.

If they're lucky, and don't learn about the history of capacitors (and the science behind them) from you, then at best, the Leyden jar may be mentioned in passing in their history class (perhaps as a quick blurb next to discussion on Franklin's experiments with static electricity), and another mention on charges and insulators in their science classes (though both of these lessons together may be separated in time by a year or two) - and only the real lucky ones will see the connection between everything, and perhaps strive to know more.

I should hope we could do better by our kids educations.

/full disclosure: I am not a parent.

[Jassper]

Jassper:

Those are both great documents; a link to this thread, and links to those documents should be placed in the playground, probably here under a new section called "Enclosures":

http://www.arduino.cc/playground/Main/ElectroInfoResources

CSingleton:

Your comments on low-cost/low-run prototype production techniques should also be placed in the same section.

I think all of this needs to be documented there.

Bravo!

 

I wonder if you could get good results with toner?

Do your toner transfer, etch your board, then do a second toner transfer onto the traces (with a different PCB trace layout that leaves out the solder joint connections - or only clean the toner from the etching off of the holes/vias?); solder your board, then laquer it (if needed)...?

Another option might be to paint the traces with clear nail polish after etching (leaving solder joint areas alone). Or how about this idea (not sure if it would work): clean the board well after etching, then put vaseline on all of the areas where solder joints would be, then spray with laquer, let it dry, then remove/clean the vaseline, etc off (the laquer shouldn't stick in those places) with rubbing alcohol or something - then solder the board?

There's got to be other cheaper and easier options out there that hobbyists can perform to keep homemade PCB traces from oxidizing...

 

Another solution (so to speak) is Seno 3211.

Does anyone know where you can get this in the USA? I see tons of stuff for MG Chemicals (coatings and such), but nothing for Seno products (or should I be looking for something else?)...

 

The 55 gallon barrel idea sounds workable.

As far as things to add in-circuit, you'll want a blocking diode to prevent the battery discharging thru the solar panels at night/cloudy days. You may want to go so far as to look into actual charge controllers, though I don't know if 24 volt controllers exist or not (I think they do). This would provide all of the reverse current, polarity safety, etc stuff in a small box. You might also be able to find a schematic for one on the internet as well.

An inverter/boost circuit could be made - basically you would make a 555 timer circuit to chop the 12 VDC (via a power transistor) into on/off pulses, then feed that into 2:1 step-up transformer to bring it up to 24 VAC - the problem will be finding such a transformer, but they do exist. Worst case scenario, you take a large bolt and wind a bunch of turns of wire on one end, and then double that number on the other end (but I can't guarantee how well it would work); you could also rewind the core of a regular transformer if you wanted to as well.

Something I am wondering, though - why are you going thru all of this trouble (unless your house is really far away from your garden) when you could trench and fill a conduit with AC wiring to your shed? It isn't that difficult provided you have an existing circuit that can handle another socket (or you can install another breaker, or add a second breaker box).

Another possibility would be to rewind the solenoid for 12V operation (although I don't remember exactly what the difference is between a 12VDC and 12VAC solenoid - I think the AC one has a holder magnet in the well of the solenoid or at the end of the plunger that prevents the "buzzing" vibration without it)...

 

In theory, yes, you could "center tap" one of the batteries to provide 12 volt power; you might want to place the batteries in some kind of vented enclosure with some silica gel in a cup (use that "pearl" cat litter) to reduce the humidity in the immediate environment, though.

As far as batteries wearing differently "in series"; this can be an issue if the loads on one or the other batteries (in your center tap scenario) is high and draws more from one than the other; but alone, together, there shouldn't be an issue. Now - if you were paralleling the batteries, and they had different voltages and such due to age - then that could be a big (and possibly explosive) issue - but that isn't the scheme I am talking about.

Given the environment you are talking about, you may want to seriously consider SLAs instead of regular car batteries - they are healthy to be around, they can leak and vent liquid, etc; if you do insist, though, put them in their own separate and clearly marked well vented (to the outside; you may also want to use a brushless DC fan to help vent any fumes/gasses built up) battery box, with a bottom tray made of plastic to contain any possible spills or leaks. Do a search on ham-radio and solar battery box construction; plenty of information on how others have done this safely.

 

Your answer seemed to concern the conversion of 24v to 12v, but I'm actually trying to power a 24v solenoid valve using 12v lead-acid car battery.

Is there any particular reason you are using a car battery, instead of something like a 12 volt SLA (sealed lead acid) battery?

If you need 24 volts, why not wire two batteries in series, and charge them with two solar panels in series? Other than the extra room that would be taken up by the batteries and panels (though if you used SLAs, you could get two 18AH SLAs (like this one):

http://www.allelectronics.com/make-a-store/item/GC-217/12V-18AH-SEALED-LEAD-ACID-BATTERY/-/1.html

...in the space that a single car battery would take up, plus they would be safer to have and use outdoors (being sealed and not having a liquid electrolyte).

 

There MUST be a "tinkerer"  gene we have that contains a "recycling" aspect that makes us look at old defunct stuff and say... I need to save that and see if I can salvage the good stuff out of it.

Resisting it is nearly impossible for me - especially if it is something that I don't know if I will run across again. Just this weekend I had to pass up two different ebay auctions (one for a ton of old components, and the other for a parts-only Big Trak; I hope that one went to a good home) because I had already spent too much, bills were due, and I really don't have the room (but I coulda fit it somewhere!).

I had already bought on eBay an old "parts-only" Armatron, that I hope to (someday) build an interface to (likely using the Arduino, based off the Popular Electronics schematic I have from the mid-80's - maybe adding feedback pots as well).

When "bulk-trash pickup" comes around in our neighborhood, I am always spying other people's junk to see if there is anything I want (it doesn't have to be robotics or electronics related either; I have been known to pick up old steel parts for welding, as well as old wood or tree limbs for burnin'!).

Get me into a Goodwill and there is no tellin' what I will bring home (for instance, this weekend I spent 2 dollars picking up an old Polaroid Sun 660 for the ultrasonic sensor).

All I need is infinite cash, infinite time, and no job...

 ;D

Once I have secreted my new contraband past my wife and safely made it down to my workshop

LOL  ;D LOL

You sound like me!

Yes; they are called Inventory Management Systems - they range in price from "free" to "2nd Mortgage on Home" (really, though, those are for business to business transactions).

Check around; here's one I found that is free and -extremely- basic:

http://asset-tracker.sourceforge.net/

Here's another:

http://www.inventory-management.org/

I am sure there are tons more; I've never used any of this software, but I am seeing that I face the same dilemma as you. Solutions exist, though...

 

Yes, we are.  I'm talking about shelving like this mounted with clips like these.  The shelves themselves would be OK if they were lined and had a decent support system.

Hmm - I have those in my house; installed them in the laundry room (where they hold a bunch of our small appliances and laundry stuff), plus some in my office closet (where they hold numerous boxes and such). They've only been in place for about 6 years now...

Hmm - I'll have to keep an eye on them...

cr0sh has some good points (but I disagree about the pegboard - it's a huge waste of surface area, compared to drawers/shelves/etc.  I'm pulling it down in my shop).

I guess it depends on what you are doing (to each his own, too!) - in my shop, I put all my "mechanical" hand tools on the pegboard; everything has a spot, and things are mostly grouped (cutting tools in one area, drills in another, screwdrivers elsewhere, etc). This is all on one of my walls (4 x 8 worth of pegboard). I have another small section (less than 2 square feet) near where my "soldering station" is at - I hang my small screwdrivers and component cutters, etc there.

Since I do a lot of mechanical work (plus household chores and welding, etc) - I need those tools out in the open for quick grabbing, without resorting to sorting through a toolbox or drawer. Plus, it makes it fairly easy for my wife to use something like a handsaw or such easily. My powertools are on a shelf above the pegboard (though my heavy power tools, like my skil saw, scroll saw, and milling machine - are elsewhere, closer to the ground). The only tools I don't have in my shop are the ones I use on auto repair; those stay in the garage (about the only one I wish I did have, which I may get a small set of, are my sockets - all I have in my shop are small sets for small nuts and bolts, but there have been times when I've needed something larger).

Definitely don't get cheap on the furniture and shelving.

You can cheap on the furniture; if you know where to shop (like Goodwill and yard sales) - sometimes you find some of that old 1950's metal stuff going for nothing!

But the shelving - yeah, don't cheap out. Get some of that heavy duty garage shelving; I made that mistake the first time around (I used shelving L-brackets and plywood) - it couldn't take the load and was about to collapse when I replaced it. Then again, I probably have too much crap. I did save the plywood for the shelves above my workbench - it wasn't bowed or anything from the weight, it was the L-brackets failing under the load. Good 3/4 inch stuff, so I wasn't throwing it away. With the rails and shelving brackets above my bench, I can darn near climb on it, now.

I like fishing tackle boxes like these for the plastic storage boxes.  It's like several small boxes in one, and you have some reconfigurability.

I had such a box before; if you are constantly moving things, or taking things "on the road", they can certainly be useful - but their opaqueness always left me desiring something else.

I'm ambivalent about the boxes of small drawers for parts. I've got one, and got stuff in every drawer, but there's plenty of unused space.  I'm thinking of a rack of storage boxes instead (got plans to build the rack, just haven't had time yet).

I've found them useful for just about everything, with the exception that I don't have enough of them to properly separate the parts out (I wish I had one drawer for each resistor value and type).

 ;D

Provided they are labeled properly (this is the big step - buy a label maker if you use these cabinets), and organized well (group like parts drawers together - ie; passives, actives, ICs, semi-conductors, etc), they can work well (at least they have for me). For larger parts (larger motors, PCBs, etc) I use clear storage boxes of various sizes (for instance, I have a couple of large clear storage boxes for storing computer motherboards).

For components, small parts, and small projects I use tackle/storage boxes (Plano 3700 series is my favorite).  An Arduino with a shield or

These work pretty well, too; in fact, I plan on getting a few more for some of the more common parts I use in prototyping, keeping the rest in the storage cabinets. I also have found such boxes (especially the ones with handles) to be useful for small tools and the like (like Dremel components).

two will fit in a 3730 compartment, and components bagged in small ziplocs which are grouped by size/type/etc will store quite efficiently in there as well.

Ziplocs are great for small components and other parts; I use them all the time as well (they came in handy once for sorting a bunch of mixed parts I picked up as scrap). I also typically use them for keeping parts of items I have taken apart together, if I plan on reusing the item or putting it back together.

Like I said before, though - to each his own and what works for him (and for what they do, of course)...