relay

181 Articles

Doorbell Combo Lock Can Open Your Garage Door

August 2, 2010 by 24 Comments

Sometimes I get enough away from writing about other people’s accomplishments long enough to actually do my own hacks. Most recently I developed a combination lock that opens the garage door. The idea isn’t original, it is based on [Alan Parekh’s] button code project, but I did develop my own hardware and software. A four digit code is entered by pressing the button a number of times for the first digit, and waiting for a flash of an LED inside before moving on to the next digit. If the correct code is entered the door opens.

My version centers around an ATtiny13. I originally downloaded [Alan’s] code in hopes that I could port the PIC firmware over pretty easily. Unfortunately it was written in BASIC so I just took what I knew about the interface and wrote my own program. I developed on an ATmega168 so that I would have no trouble running out of programming space, and was able to optimize my code down to 964 bytes to fit on the tiny13.

The hardware is quite simple. I purchased a lighted doorbell from Home Depot and swapped out the light bulb for an LED. I choose this because the doorbell mounts in a 5/8″ hole in the trim of the garage door and is easily overlooked. I’m quite happy with the results, and if you want to play around with the idea, you can easily build the circuit on a breadboard and use another LED for the load rather than including a relay. Hit the link at the top of this post for the schematic, code, and build images.

Air Freshener Hacking

July 27, 2010 by 34 Comments

In an effort to improve his marital standing [Tech B] hacked an air freshener to make it Internet controllable. The main component here is a Glade Sense and Spray. It cost him $7 and is meant to spray out some sweet smells when it senses motion in the room. The unit also has a manual spray button which he patched into with the help of a relay. From there some Arduino code and an IRC bot take over, letting him unleash freshness from anywhere he has IRC access.

When reading about this we were also thinking: “motion sensing circuitry available at local stores for just $7?”. We may have to conduct an investigation into the alternative usefulness of that package.

If you have another brand of automatic freshener around it should be just as easy to hack as this one was.

Power Cycling A Problematic Modem

June 29, 2010 by 53 Comments

[Gigawatts] struggled against a shoddy Internet connection for quite some time. Changing modems, having the line serviced, and spending far too much time on the phone didn’t do any good. In fact, the only thing that fixed the problem was power cycling the modem once it stopped responding. His solution was to automate the power cycling process. He added a cron task to his router which is running DD-WRT, a favorite firmware alternative for hacked routers. The script monitored the WAN connection and when it went down it would toggle one of the serial port pins. He whipped up an outlet box with a relay in it and used that serial pin to cut the power going to the modem. A workaround yes, but it was the only thing that brought an end to his frustration.

Lunkenheimer Steam Whistle, Doorbell

May 16, 2010 by 30 Comments

We’re going to straight out agree with [Pete] on how surprisingly quiet doorbells are now a days, and if we had it our way we would put his Lunkenheimer train whistle doorbell in every home*. The setup he uses is surprisingly simple, opting for a pre-built wireless doorbell that signals a microcontroller which in turn drives a relay and solenoid. While he does include a video, we felt it didn’t quite show the intensity of these whistles.

*HaD is not responsible for hearing loss and subsequent melted brains.

Strobe Array For Dance Parties

April 9, 2010 by 34 Comments

[vimeo http://vimeo.com/10722768%5D

Check out this slick strobe array for dance parties. Controlled by a DMX512 interface, only a small modification was necessary to get the strobes working. If you’ve played with a small commercial strobe light, you’ll know there’s a potentiometer to control the strobe speed. He simply soldered a relay after the pot. This allows him to tune them to be charged and ready for when the relay is closed.

[via HackedGadgets]

Pre-spun Hard Drives

February 5, 2010 by 56 Comments

This device is lovingly called the SPINmaster. [Linux-works] built it to spin up multiple hard drives before the motherboard starts up. It detects the power-up from the PSU and uses a relay to hold the motherboard in reset, indicated by the red LED. Each of four relays then spins up a hard drive and illuminates the green LED when ready. Once all green lights come on the reset relay shuts off and the bios starts up. This type of staggered startup takes a lot of the load off of an under-powered PSU. He’s posted firmware and there’s a schematic available too. We took a look at his video but there’s not much to see as it’s just the inside of the machine while it boots up.

Arduino Traffic Light

January 5, 2010 by 28 Comments

[Rockwell] sent us an update on his traffic light hacking. Dedicated readers will remember seeing this legally attained traffic signal controlled through a parallel port from back in 2005. The new update swaps the old port for USB and adds several autonomous functions which are demonstrated in the clip after the break. The update includes a nice UI and some notifications for things like email, IMs, Reddit posts, etc.

He’s given control of the hardware over to an Arduino. Instead of building the board into the project he’s included just the parts he needs; an AVR running the Arduino bootloader, a crystal and filtering caps, and an Arduino serial to USB module for connectivity. The AC load switching is handled by three relays. The relays he links to are 12VCD rated coils. We think this should have pointed to 5VDC coils as that’s the voltage that the logic circuit are running at. Be careful with switching these AC loads, this traffic light isn’t a toy.

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