Tag Archives: Tinkering

DIY Automatic Cat Feeder

So, our cat Mohinder is a growing boy.  He wants to eat constantly.  It’s not actually constant eating of course, but he always seems to be hungry when we want to sleep.  Madeline has become patient with our sleeping/feeding schedule but Mo is terribly persistent about eating whenever he is hungry.  Typically, he will jump up on the bed and carefully grab a bit of Emily’s hair in his mouth and gently pull it.  It’s not meanness and it doesn’t hurt, but it is annoying to be sure.  Of course, I have no hair so he can’t wake me in the same way.  On the few occasions he has picked on me, he gently nips on my nose.

Electronic parts for the automatic cat feeder

As you can imagine, that has gotten pretty old so I started to tinkering.  I am going to post some ideas that I am fooling with and will show the finished product at a later date.  The basic idea I am working with is to have a digital alarm clock trigger some electronics to open a stripped down computer cd-rom tray.  I think the mechanism on a computer cd-rom is pretty nice and will work perfectly as a gate to let the cat food fall from a hopper into the cat bowl.  I started by salvaging an old cd-rom from the junk bin at the office.  I stripped all of the electronics out of it (basically, I just pulled off anything that wasn’t the mechanical stuff that opens the tray.  With a little experimentation using a 9-volt battery, I was able to find the motor that drove the gears to open the drawer.

The cd-rom motor to open the automatic cat feeder

I bought a new alarm clock to trigger the electronics to trigger the motor that opens the cd-rom.  I opened the alarm clock and found the wires that connect to the speaker for the alarm.  A quick hole in the sidewall of the clock allowed me to pass the wires from a 9-volt connector to the wires that used to connect to the speaker.  I closed the clock back up and was able to measure the current in the 9-volt connector when the alarm was (silently) going off. In other words, when the alarm goes off and would normally sound the alarm, it now send an electrical pulse out through my 9-volt connector which runs outside of the clock.

The alarm clock to trigger the automatic cat feeder

My plan is to have the power from the intercepted alarm signal drive a relay which allows a larger current to pass through it and a transistor.  The relay and transistor work as a basic switch to send power to the cd-rom motor.  I wired this all up last night and all of this stuff works just fine.  I am sort of experimenting now with how to get the drawer to actually deliver the catfood.  My plan is to have the drawer push open a slide or else be the slide that opens the hopper of food.  The real challenge is to figure out how to make all of this stuff cat-proof.  Mo is persistent and has a lot of free time and has gotten in to the most unusual things. Anyhow, these pics are an overview of the project, meant solely to both confuse and amaze.  I’ll post the actual schematic and the finished product another day when I get it all figured out.  Anyone have any thoughts about cat proofing stuff?

Refrigerator marble run

Our refrigerator

Like many refrigerators I have seen, ours is an exercise in chaos.  Both kids pretty much get the alphabet now but we’ve retained the magnet letters for some reason.  We occasionally form up some clever words but there is a limit to what can be spelled out.  In addition to the letters, the refrigerator serves as our command center of sorts.  All things kid-related are stuck to the front door, held in place by magnets that are one sheet of paper from being over-taxed.  Mo, one of our cats, seems to always push the envelope of magnetic tolerance and periodically clears the lower reaches.

Marble run on the refrigerator
I came across this post and it seemed like the perfect change…the fridge was just crying out for a change.  I junked a bunch of stuff and threw this marble run together pretty quickly.  Hot glue + magnets + plumbing odds and ends = fun!  Abigail and I messed with it quite awhile after supper until bed time.  I am sure that we’ll mess with it more this evening.

Marble run on the refrigerator
She was pretty quick to get the point of how the marble we were using knocked down through the system.  Unfortunately, she also had to see the underside of our oven and refrigerator as we tried to recover renegade marbles that understood physics better than we did!

Marble run on the refrigerator
Mo our cat was, of course, terribly interested in the entire bit of fun. He kept standing under the outlet and got thumped a few times watching the marble come down!

Catapult of awesomeness

Catapult parts
My wife accused me of trying to be Jack Black with the title of this post. Although I do look pretty fantastic in wrestling tights, I don’t have his kung fu or guitar skills. Instead, I have to rely on my skills with a hot glue gun. This week I have posted about all sorts of domestic stuff so it’s about time for a little manly mayhem!

Homemade Catapult
The kids and I made a catapult last night. I recently finished out a bottle of medicine and hated to see the bottle just go into the recycle bin.  The bottle is just too pretty… I mean, the color  instills fear in the recipient of the catapult’s action! Anyhow, with a few minutes, a couple of pieces of scrap wood and a hot glue gun, we made a catapult which we used to launch Jolly Ranchers into Isaac’s mouth.

Homemade Catapult at the ready 

We had to mess with the angle of the base to get better distance, but Isaac was willing to dive for a few until we figured it out.  We found that by lifting the back of the base, we could launch a Jolly Rancher quite a distance. As part of the fun, we learned some about the physics of catapults and also the history of seige warfare.  Isaac knew that the spring stored energy when flexed.  We talked about momentum and kinetic/potential energy.  It was a pretty quick project and I think we all learned a little too.  I think we may try a trebuchet this summer.  We have a compost pile ripe for attack!

I think we’ll revisit this project in a few years and do a little experimentation.  I would like for us to experiment with the length of the catapult arm, the angle of the base, the tension of the spring and the distance the arm can travel.  I think we are a little young for too many calculations, but we may try this outside this summer with a bigger setup that we can really play with!

Knitting on the cutting edge

Knitting a hat on a loom

It’s been cold here and I have such a delicate, pretty bald head.  Without hair, I never have to worry about messing up my do or getting hat head.  It does leave me with a heat radiator in the winter and an overactive solar panel in the summer.  Out of necessity I have a pretty fair collection of winter hats.  I was reading Children in the Corn’s blog several months ago and she posted about knitting winter hats on looms.  I had never heard of loom knitting but I have tried regular knitting and hated every minute of it (and I spent at least 4 minutes trying…most miserable 4 minutes of my life).  Anyhow, loom knitting looked pretty cool and I figured it was a new fangled thing.  I was dying to be at the cutting edge of knitting technology!  I found the round loom set by Knifty Knitter at several locations but I was especially happy to find it half price at a local craft store.  I picked up the 4 loom set for $7.50.  That prompted me to do a little research on loom knitting.  It turns out that loom knitting has been around for a long time , possibly since the 1300s .  Awesome!  I wanted to be a part this ancient art…no need to fool around with the modern stuff…new fangled knitting technology has no place in my home!  Well, you know how it goes.  There isn’t much new under the sun.  I thought I was getting into something new and cool, but instead, I am getting into something old and cool.

Hat knitted on a loom

I posted about my first knitting experience a few months ago.  These new looms are of the same type as the first one I tried but are much larger (and more powerful of course!).  I decided to use my new looms to make a black hat to keep my bald head warm this winter.  I used regular medium weight black yarn.  To make it thick enough to keep the cold out, I used two strands of yarn at a time (i.e. I just bought 2 skeins of yarn and double wrapped each post of the loom).  I knocked out my first hat in only 6 weeks.  It really only took me a few hours but, like all of my projects , I stretched it out over a sufficient period of time so as to keep my wife guessing.

My loom knitted hat...worn by a crazy man!

I am pretty happy with the way this hat turned out.  It is pretty warm which is requirement #1.  The other requirement is that it be cheap.  I seem to change hats like I change underwear..at least once every few weeks.  I just cannot seem to keep track of hats.  They always turn up again, but I hate going outside in the intervening days.  Since I can now whip out hats in 3 hours to 6 weeks, I no longer am worried about keeping track of my hats!

Cookie tin banjo

My homemade cookie tin banjo!

I was browsing through some old Firefox books a while back when I came across some folks talking about making banjos and dulcimers.  In particular, one fella talked about making a cookie tin banjo.  I had 4 cookie tins in my office that I saved after we emptied them last Christmas which seemed perfect for the job.  So, since I had one insignificant piece of junk I needed, I felt compelled to find the rest and build a banjo!

For the neck of the banjo, I used an old piece of bamboo flooring which I glued to a pine 1×4.  The floorboard by itself was not thick enough to provide support where it enters into the cookie tin.  I am not exactly sure that it’s the right thickness now but it seems to fit in my hand ok.   I left the bamboo top squared off but I rounded the back (the pine part) off smooth so I could hold it easily.  Now, I know you are curious how I came up with the shape for the peg head…I traced two Mt Dew cans.  This part is important…you have to use Mt Dew to get the thing just right.

My homemade cookie tin banjo!

My homemade cookie tin banjo!

The tail piece is a chunk of an extra slat from plantation blinds we installed last Summer.  I think there must be a proper way to do this but it seems that the only measurements that really matter are the distance from the bridge to the nut (basically, from the wooden peg on the face of the banjo to the point where the neck joins the peg head.  My homemade cookie tin banjo!

My length is 25 inches though there is some flexibility in that size.  The distance from the bridge to the 5th string which attaches to the side of the neck is 18 1/2 inches.  Just about everything else negotiable as far as I can tell from reading in Firefox 3.

The hardest thing for me to do was carve the tuning pegs.  I tried using steel thumsbcrew and eye bolts and regular screws but none of those things would hold the string tight enough to tune.  That left me with carving wooden pegs which hold their position by friction.

My homemade cookie tin banjo!

My homemade cookie tin banjo!

I bought square 1/4 poplar dowel rods and cut off 2.5 inch sections to carve the pegs.  I rounded the bottom 2/3 of the peg to fit in the hole.  The top part I left square so I could get a better grip on it for tuning.  It seems simple enough but it was a real drag to carve them round.  My hands are killing me from messing with those tiny pegs.  Anyhow, I drilled a small hole in each to catch the string and they seemed to tune and hold pretty well.

My homemade cookie tin banjo!

I have a chromatic tuner that I got to tune my violin.  I messed around a bit to get the tuning right for the banjo.  I think it is pretty close although the 4th string doesn’t sound right to me.  We’ll see.  It definitely has a banjo sound.


So, the $6 Martin banjo strings are about the only money I have in this thing.  Gosh, if only I had any idea how to play a banjo!

Solar Furnace – Results

Solar furnace installed

We finally had a sunny day yesterday and I was able to get some real results from my solar furnace .  I had to make a few changes for success though…

First of all, I discovered that the mercury switch was not sensitive enough to really work.    The cold air outside was messing up the way it functioned.  I could not insulate the part of the air box where the switch was since the switch has to be able to move (if you’ve never seen the setup, a mercury switch is placed on a temperature sensitive metal coil which moves and allows the mercury to open or close the switch).  I decided to experiment with wiring the solar panel straight to the fan which actually worked very well.  The fan only came on when the sun was out and shining pretty brightly which was precisely when the best heat was being made.

The pipes that run from the furnace to the house were white originally but it seems that enough cooling took place in the pipes to make the system not work as well as I had hoped.  I painted them flat black like the rest of the system and it worked like a charm.  The pipes absorbed heat from the sun while transferring the heat through the system, thus helping with the whole “hot air rises” thing.

Solar furnace installed

I also discovered that I had a few air leaks around the pipes and in the holes for the air pipes in the furnace.  I used silicone caulking (which will actually cure in about any temp regardless of what the instructions say) to patch all of the holes/gaps/leaks.

Once I made those three changes, I took temperature measurements of the cool air pipe from my family room floor and the warm air pipe from the furnace.  My floor air was 63 deg F and my warmed air was 84 deg F!  Hee-haw!  Eureka! Ding Dang, y’all!

Ok, so I was pretty happy with the results.  The fan kicks on and off with the sun which manages the heat pretty well.  I still need to boost the power to the fan to get a little more air flow.  I did some experimenting and was able to get a better temperature rise with a bit more air flow.  I will probably add another cheap-o solar panel to run the fan better.  I also need to find a better way to prevent backflow.  I really don’t like hanging a piece of plastic in front of the vent.  For now, it is working but I don’t like it as a long term solution.   I have glass to build one more furnace so I will probably build it out then figure out some way to deal with both systems.  Anyhow, for now, I am pleased with the solar furnace!

Solar furnace installation

Solar furnace thermostat

I last posted a week or so ago about my solar furnace.  I mentioned that I needed to install the system in my window and get the fan/thermostat working.  Well, my friends, wait no longer!  This weekend I finished the installation of the solar furnace and even powered it with a small solar panel…but I am getting ahead of myself.

Solar furnace entry to house

My downstairs family room has 5 windows, 3 of which face southward.  A south facing panel is optimum because it gets sun almost all day as the sun progresses across the sky.  I read that 20 degrees from due south results in a 5% decrease in performance.  Luckily I have south windows but if I didn’t have due south, I would still try the furnace.  A 5% decrease would still make things interesting.   In addition to the direction, you have to consider the angle from horizontal of the panel so that it gets optimum sunlight in the winter when the sun is lower in the sky.  I have read various thoughts on the optimum angle but the easy one for me to remember is “latitude + 10”.  Here in Charleston, our latitude is 38 degrees.

Solar furnace entry to house

According to this calculation then, the optimum angle from horizontal is 48 degrees.  Using my trusty eyeball, I leaned the solar panel along the south wall of my house and tilted it at precisely 48 degrees.  To be more exact, you should consider doing a site survey to make sure you really have things right. I will probably just mess with it until it gets the best sun. In a more permanent installation, you would want this to be much more precise. Mine is easily movable.

Anyhow, I built a box (which I insulated) to run a warm pipe and a cool pipe through my window.  The thermostat and fan are inside the warm pipe inlet so the warm air should automatically rise and slowly flow across the thermostat.  The rise in temperature should kick on the thermostat/fan and move the air a little better through the system.  As the warm air evacuates, it will cool the thermostat and turn off the fan.

Solar furnace entry to house

I mentioned in the last post on this topic that I could not drive the fan with a super cheap solar cell.  I was rummaging through the junk bin at the office when I found a pair of fans (actually, quite a few fans) that were lower amperage than my original one.  Anyhow, my new fan is rated at 12 volts and  0.16 amps.  I know it will run at 9 volts so I figured I needed a solar panel that would produce 1.44 watts (i.e. 9 * 0.16).  Harbor Freight sells a solar panel used for trickle charging auto batteries for $19.99.  Actually, the website has it for $14.99 but in the store it is more.  If I would have taken the printout to the store, they would have reduced the price.  Apparently the store and website are somewhat independent.  I didn’t have a printout and it wasn’t worth driving back for it so I paid $19.99.  Ok, back to the story – it will produce 1.5 watts which will run my new fan.  I don’t know if it always just produces 12 volts and the amps vary (because it produces differently depending on the strength of the sun) or if it produces 0-12 volts and constant amps, etc.  All that is to say, I don’t know exactly what wattage is driving my fan but it turns it.  Solar furnace entry to house

It occurs to me as I write this that I should measure the output with my mulitmeter…but really, for now, I don’t care.  The fan turns fine in sun and that is my main goal.  Unfortunately, the fan will not blow the dryer vent louver open. I had planned to use a dryer vent to close the inflow when not in use.  I will have to resort to the “plastic over the hole” method I mentioned in the earlier post, to prevent back-siphoning.  And let me tell you, back-siphoning is real and a problem if you don’t deal with it…I quickly learned a lesson on that topic!

Ok, lots of words to describe all this.  The only problem is, I have not had a sunny day since I got this thing installed.  I wanted to post about this progress but I don’t have any real results yet.  I will have to post again with results.  I know it will make a difference, but I don’t know the extent.  Stay tuned!

Junk vibrobot

Junk vibrobot

There is a category of electric critters called vibrobots.  I hesitate to call them robots , but I guess they are autonomous moving things.  Anyhow, as usual, I have bits of junk laying around that tend to rear up and get in the way now and then.  I have an old motor I salvaged out of a vcr or something.  I also had wire insulation hangers from my crawlspace insulation project.  That’s about all you need to build a junk vibrobot.  I bent a paperclip in an L-shape and taped a screw to one end of it.  The screw attached off center of the motor shaft throws the balance of the motor off so it vibrates.  Since it is attached to rigid, skinny wire feet, the vibrations through those feet on a hard surface translate into motion…random motion!

Junk vibrobot

So, I zip-tied the end of the paperclip without the screw to the shaft of the motor.  I then bent the insulation hangers in an arc and zip-tied the 2 sets of legs around the motor.  I hooked a 9-volt battery to the motor contacts and away it went.   I tried putting little rubber feet on it but the bare wire on hardwood jittered the best.

Mo, our silly cat had to get in on the fun.  The kids had a blast running the v-bot around Mo.  They had it timed perfectly so he would jump in the air when it started spinning.  For a cheap toy, it was quite a bit of fun!  Just a word of warning though…if you do this on your dining room table, be sure the cat is not around.  Also, be sure your wife is not around as she will not be impressed with the cat on the table or with the little scratches the v-bot feet leave.  Of course, this is certainly not the first time I have scratched the dining room table…but that’s another story.

Click the image for a short video

Here are some other vibrobots that other people have made.  I have seen some that are solar powered, some that look just like bugs, and some that are made or worse junk than mine.

Itty bitty vibrobot
Minty vibrobot

Solar Furnace – thermostat

Old wire thermostat

Earlier this week, I posted about my solar furnace project.  I can’t take all the credit for the idea of a solar furnace as they have been around for a long time.  Most of them seem to be passive – relying on natural motion from the warm air rising through the system.  This sort of air flow is not typically very strong (though it can be), so cannot open a louver or check valve.  Just leaving the hot air pipe open is an option though physics will bite back at night or when it is not sunny outside.  Just as hot air rises, cool air sinks so at night, warm air will syphon from the house backwards through the system.  Some folks drape a piece of plastic over the warm air output so that the warm flow blows the plastic open a little.   Cool air cannot flow back through the plastic, supposedly.

Thermostat for solar furnace

All that sounds nice, but I cannot be satisfied with simplicity when I can further complicate things with technology.  Being interested in saving a buck and doing the right thing energy-wise, I replaced our old thermostat with a digital programmable one a couple of years ago.  I noticed that the old thermostat had a mercury switch so I didn’t want to just throw it in the trash – instead I kept it in my stash of junk…and lucky I did.  This project is prime for my sort of junk.  I stripped the mercury switch and the bi-metallic temperature wire from the thermostat and connected it to an old computer fan.  I am building a box that will contain the thermostat and the computer fan.  The fan will pull warm air from the furnace across the thermostat.  While the air is warm, the mercury switch will turn on the fan which will blow open the dryer vent (that will prevent cold-air backflow) and send warm air into my room.

Thermostat for solar furnace

Initially, I had planned to power all of this with a solar panel.  My fan is a 12 volt, 0.62 amp fan (though I ran it just fine with a 9-volt battery).  To drive the fan directly from the solar panel (at 9 volts), I would need a 5.58 watt panel (watts = volts * amps).  I may be able to get away with a little less but the cost of a 4-6 watt solar cell would still cost somewhere around $50.  I have various 9 volt wall-wart transformers from old gadgets that I no longer need.

Louver for solar furnace

For now, I will just drive this system from wall power.  At 9 volts, when the fan is on, it will draw around 4-5 watts – about the same as a nightlight.  I can live with that.

My plan is to get all of this hooked up and running this weekend.  I will post again with the final project.  It is supposed to be cool this weekend so I guess the timing will be right!

Spammers have been attacking this page so I have turned off comments.  If you would like to have a discussion, please post on one of the other solar furnace posts or send me an email message.  My contact info is in the “about/contact page”.  Sorry for the inconvenience.


A salty bunch

Microscope work

We gathered a jug of salt water from the ocean 2 years ago on a trip to Tybee Island near Savannah, GA.  I had in mind when I collected it to do an experiment to show the kids how to separate the salt from the water, how crystals formed, how to research stuff, etc.  I finally got around to it last weekend.  We did several experiments which have had mixed success.  First, we looked at various things under the microscope including epsom salts, table salt, and sugar.  In our first experiment, we suspended a string in a cup full of ocean water.  No crystals formed on their own so we are waiting on evaporation to expose the salt.  We also mixed epsom salts and water to form crystals.  This was sort of cool but not as dramatic as I had hoped.

Making salt crystals

Next, we supersaturated water with table salt.  Crystals have definitely formed on a suspended string.  Crystals have also formed on the side of the jar in which we are doing our experiment.  We put a bunch of salt in that jar so the effect is pretty dramatic.  This was closer to the effect for which I was hoping.

Both of these experiments were pretty slow to show much effect for kids though.  Being anxious for my kids to ohh and ahh at my scientific knowledge and ability, I found a recipe for making crystals from salt, liquid bluing, and ammonia.  making salt crystals

As a base, we tried to use a piece of cardboard rolled up in a tube.  My expectation was that the cardboard would wick up the water and make a little crystal tree.  For some reason, the cardboard did not wick any moisture.

Mrs Stewart's crystals

I guess it was too dense (or maybe I was?) so the crystal tree turned into more of a crystal shrub.  Still, the effect started within a day or so.

Anyhow, here are some additional methods to make crystals.  The kids were in to it for awhile and had a good time checking on the progress.  I’d recommend it for your own edification as well!


making salt crystals