|Posted on Friday, October 25, 2002 - 09:51 pm:||
After building my first terrarium it became readily apparent that I would need at least one timer if my setup (using an ultra sonic humidifier) was going to be successful. I did some research into timers and found that most people were using household light timers available at most hardware stores. The problem I had with these is most of them don’t offer many options. They vary from 12hour on / 12hours off (cheaper models) to 1 hour on / 1 hour off (more expensive models). This was not near the level of accuracy I was looking for. I checked out digital timers but found most of them were well out of my price range. I wanted something that would be accurate to the minute and under $10. I inevitably concluded my only solution was to build one. The purpose of this guide is to help others construct a very accurate timer for under $10 using only readily available items.
1 normal analog clock with mettle clock hands (the hands MUST be mettle).
Some phone wire or any other type of electrical wire (cat-5 network cable works great).
1 extension cord (any length).
Steal wool or fine sand paper.
1 9 volt battery.
1 relay (radio shack part number #275-248 or #275-248a) - $3.99 (available at any radio shack or from www.radioshack.com).
If you don’t have a clock readily available try Salvation Army or a garage sale. You can probably pick one up for next to nothing (maybe old and ugly but that’s ok – so long as the hands of the clock are mettle). If all else fails Wal-Mart caries a large selection of cheap clocks.
The first step is to disassemble your clock. The goal is to take the cover (protective glass) off the clock and remove the clock hands without damaging them. Take the minute hand and use sand paper or steal wool to sand off the finish on it (most mettle is finished so that it doesn’t rust – however this can interfere with its ability to conduct electricity).
Next take a 8” piece of wire and tape it to the face of the clock as shown in this picture
You should leave the wire as long as possible (it will be trimmed latter). The trick here is to bend the wire in such a way that it is only slightly higher than the height of the minute hand so that when the minute hand moves around the face of the clock it will come in contact with this wire for a period of time. Now connect this wire to one of the coil inputs on the relay (doesn’t matter what one).
Next take a second piece of wire and tape it to the side of the clock face and bend it such that it comes in contact with the center of your clock hand (this is a bit tricky but can be done with a little patients.) The goal here is to position it so it doesn’t interfere with the movement of the hand but allows electricity to flow into the clock hand.
Connect this wire to one end (doesn’t matter negative or positive) of your 9 volt battery.
Next you want to connect the other end of the 9 volt battery with a wire to the other coil input.
Now take the extension cord (in the middle somewhere) cut one wire (don’t cut though both like I did in the pic as you will just have to reconnect it) and attach the relay into the extension cord as pictured.
For those that don’t know what a relay dose is it basically allows a small amount of current to turn on or off a large amount of current. It wouldn’t be safe to run 120VAC though the clock so we run 9V though the clock and when the hand touches the wire it creates a complete circuit which triggers the relay to allow the current from the extension cord to flow though it. When the clock hand moves past the wire the circuit to the relay is broken and the relay stops allowing electricity from the extension cord to flow though it, turning on or off whatever you have plugged into the extension cord.
The last step is to test it out. Simply plug the plug of the extension cord into a wall outlet and plug a light (be sure the light is on) into the other end of the extension cord. Now set the clock 1 minute before contact with the wire and wait and see. If everything worked correctly the light should turn on when contact is made and off when contact is broken. You can very the length of the wire to control the amount of time you wish the light to be on. Be sure to use electrical tape to tape over all the exposed wires. Don’t want anyone getting electrocuted.
You can plug any device into the extension cord. If you cord allows you can even plug in more than one. I currently use this setup on my cool mist humidifier and have it running for 5 minutes every hour.
If you require different timing intervals you can easily use more than one wire. If you wanted your device to go on 2 times an hour just use one wire at 12 oclock and the other at 6 oclock. You could also use the hour hand instead if you wanted a much slower timer interval.
The author of this document bears no responsibility for any damages or injury caused by the above guide. Please be very careful when using 120VAC and be sure to test your device for fire hazard. Never leave wires exposed as in the pictures (this was done to better illustrate the connections – all wires should be covered with electrical tape). This guide is meant to illustrate the construction of a timer and in no way does its author support or condone the its use in any illegal activates.
|Posted on Friday, October 25, 2002 - 10:01 pm:||
Looks pretty good (saying with a nervous twitch)
I don't mean any disrespect David as I really do appreciate the time and effort you put into this.
I just want to remind the non-techies out there that the $3 timer you can get anywhere is good for 30 minute intervals. There also is a digital timer I found at Home Depot for $20 that allows for 15 program settings, fourteen individual days, and it can be set to be on for as little as one minute.
And, as the self proclaimed Mycotopia Underwriters Laboratories inspector...be safe
|Posted on Friday, October 25, 2002 - 10:09 pm:||
yea, thats great!
but... even people such as myself, familar with electronics... wouldn't use it.
at the risk of sounding like a jerk. id rather just spend the extra 5 - 10 bucks on a store bought one.
|Posted on Friday, October 25, 2002 - 10:10 pm:||
humm i checked home depot and couldent find anything decent.. do you have a model number for your timer just out of curiosity.
|Posted on Friday, October 25, 2002 - 10:21 pm:||
Dude, I admire your level of commitment.
|Posted on Friday, October 25, 2002 - 10:26 pm:||
I couldn't find it on Home Depot's site but I saw one there last week so I know they still have them. Here is the timer available through Amazon.com: Intermatic DT11C 24 Hour Grounded Programmable Digital Timer
It is a beautiful little gizmo
J. Clay Mcwilliams (Jclaymcw)
|Posted on Friday, October 25, 2002 - 10:27 pm:||
Whats wrong with Davids homemade timer? What are the dangers?
|Posted on Friday, October 25, 2002 - 10:33 pm:||
i have to admire your ingenuity.
almost looks like something a terrorist would use for his bomb.
it's a great post for those who love to tinker and who would rather build it themselves the hard way instead of forking over their dough.
|Posted on Friday, October 25, 2002 - 10:33 pm:||
we'll keep this as archive material, just for future reference.
|Posted on Friday, October 25, 2002 - 10:35 pm:||
Nothing is wrong with it, although a little solder wouldn't hurt and I found long ago that Radio Shack parts aren't to be trusted, especially relays.
I think David did a fabulous job trying to save his fellow Mycotopians some hard earned cash
Dr. Cubensis (Shroomzilla)
|Posted on Friday, October 25, 2002 - 10:51 pm:||
All I have to say!
Is: First I was Gonna Quote Eyebooger,
THen i was gonna quote malformed instead
And then HIPPIE!!!!
DUDE!! That is some serious commitment for the Home based do it yerself GURU!!!
I take my hat off to you sir...
That is one crazy dealeo and I salute you!
|Posted on Friday, October 25, 2002 - 10:58 pm:||
yea, i loved the timer. ive done stuff like that myself.
i just wouldnt bother spending the time on it when i could go out and buy a nice digital one or something.
not to mention (exactly what was allready said, radioshack stuff is cheap)
i even wanted to mess around with programming chips.
(mod chips for game systems, etc)
couldnt order the device i needed to write to the chip because at the time i didnt have a creditcard.
|Posted on Friday, October 25, 2002 - 11:02 pm:||
yeah i am interested to see how long the relay lasts.. it will only be on for 5 minutes every hour so hopefully it lastes awhile... i was thinking of doing it with chips to.. i played with PIC chips along time ago.. but that was out of my budget for this project.. maybe next time ... if it breaks ill be sure to post the time it lasted ... for future projects dose anyone know a better electronics store wiht higher quality parts i could use
|Posted on Friday, October 25, 2002 - 11:16 pm:||
yea, the pic programmers are a bit out of my price range for this kind of basic tinkering.
anywhere from 50 to 300 bucks more you spend the better they get.
but thats how the mod chip makers make there money,
spend some money on the programmer and a box of chips, download someone elses chip code from the internet, spend a few seconds on each chip and turn around and sell them for an insane profit.
i think the going price for ps2 mod chips are like 20 bucks (and it only costs like 50 cents a chip to make them)
|Posted on Monday, October 28, 2002 - 05:11 pm:||
David, as for good electronics part suppliers go:
Mouser is my favorite for general purpose parts.
National Semiconductor is great for project specific parts. Check to see if there are free samples available for the semiconductor you want. A buddy of mine gets tons of $100 amplifier chips for free just for being an EE student. They don't check credentials. Oh, and they send them next day FedEx
My favorite discount and surplus suppliers are:
All Electronics (Better than, and not to be confused with, Alltronics)
That's about it, check em out and you will find some seriously good deals on all sorts of tantalizing projects
Dirty Wop (Anotherdirtywop)
|Posted on Monday, October 28, 2002 - 07:11 pm:||
I wish I wasn't stupid!