Kit Review – SC/Jaycar Garbage and Recycling Reminder

Introduction

Every month Australian electronics magazine Silicon Chip publishes a variety of projects, and in January 2013 they published the “Garbage Recycling Reminder” by John Clarke. Jaycar picked it up and now offers a kit, the subject of our review. This kit solves the old but recurring (for some) problem – which bin to put out, and when!

The kit offers a simple way of keeping track of the bin schedule, and is suitable for up to four bins. With a simple user-interface consisting of a button and LED for each bin – once setup the reminder can easily be used by anyone. It allows for weekly, fortnightly and alternate fortnights – which is perfect for almost every council’s schedule.

Assembly

The kit arrives in typical Jaycar fashion:

and includes everything you need, including an enclosure, front panel sticker and battery:

 The PCB is well done, and routed nicely to fit inside the enclosure:

Now to get started. The instructions included are a reprint of the magazine article, and as Jaycar have modified the kit a little, their notes and photos are also included. However there isn’t anything to worry about.

Assembly is straight-forward, the only annoying thing was the assumption that the constructor will use off-cuts for jumper links. Instead – use your own header pins:

Furthermore, when soldering in the resistors and 1N914 diodes next to the LEDs – leave them floating so you can move them a bit to make way for the LEDs:

This is also a good time to check the buttons line up with the holes drilled into the front panel (a template is included with the instructions):

At this point you can fit the LEDs to the PCB, and carefully match it up with the drilled lid. You are supplied with a red, green, yellow and blue LED – which generally match the bin lid colours from various councils. Screw the PCB into the lid then solder the LEDs in – after double-checking they protrude out of lid. Then insert the battery and make a final test:

If you made it that far, you can apply the sticker included to illustrate the front panel. To save time we cut the sticker up for a minimalist look. However you now need to set-up the jumpers before closing the box up. There is a set of three pins for each bin, and a jumper can bridge the first two or last two pins, or none. If you don’t bridge them – that bin is weekly. If you bridge the first two – that bin is fortnightly from the setup day. If you bridge the last two – that bin is fortnightly from the next week, for example:

So you can easily set it up for a weekly bin and an alternating-fortnight pair of bins. Once you’ve setup the jumpers, screw up the box and you’re done.

Operation

Once you’ve set the jumpers up as described earlier, you just need to execute the programming function at the time you want the reminders to start every week. For example, if your weekly collection is 4 AM on a Thursday – do the programming around 5pm Wednesday night – that will then be the time the LEDs start blinking. When you put out the appropriate bin, press the button below the matching bin LED to stop the blinking. You can control the number of bins – so if you only have two bins, only two LEDs will activate. The blinking period is eighteen hours, and you can adjust the start time via the buttons.

How it works

The circuit is based around a Microchip PIC16LF88 and has an incredibly low current draw, around 15 uA when the LEDs aren’t blinking. This allows the circuit to run for over two years on the included 3v coin cell battery. The internal clock is kept accurate to around 10 minutes per year using an external 32.768 kHz crystal. After a period of use the battery voltage may drop to a level insufficient to adequately power the LEDs, so each one has a voltage doubler by way of a diode and capacitor – very clever. This ensures LED brightness even with a low battery. For complete details purchase the kit or a copy of the January 2013 edition of Silicon Chip.

Now it sits next to the kettle, waiting for bin night…

Conclusion

Personally I needed this kit, so I’m a little biased towards it. However – it’s simple and it works. Kudos to John Clarke for his project. You can purchase it from Jaycar and their resellers, or read more about it in the January 2013 edition of Silicon Chip. Full-sized images available on flickr. This kit was purchased without notifying the supplier.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Australian Electronics – David Jones interviews Colin Mitchell

Welcome back

In this post I would like to share a series of interviews conducted by Dave Jones from eevblog.com. Dave interviews Colin Mitchell from Talking Electronics. Throughout the 1980s and onwards, Colin published a range of electronics magazines, tutorials and a plethora of electronics kits – of which many are still available today. Personally I was a great fan of the TE products, and sold many of his books through my past retail career with DSE. I hope you enjoy these interviews, and if not – stay tuned for upcoming articles.

Once again, thanks to Dave Jones and of course Colin Mitchell from Talking Electronics for their interview and various insights.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Tutorial: Analog input for multiple buttons – Part Two

This is chapter forty-six of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

[Updated 19/01/2013]

A while back I described how to read multiple buttons using only one analogue input pin. However we could only read one button at a time. In this instalment we revisit this topic and examine an improved method of doing so which allows for detecting more than one button being pressed at the same time. This method is being demonstrated as it is inexpensive and very easy to configure.

(For a more exact and expensive method please consider the use of the Microchip MCP23017 which allows for sixteen inputs via the I2C bus).

As you know the analogue input pins of the Arduino can read a voltage of between zero and five volts DC and return this measurement as an integer between zero and 1023. Using a small external circuit called a “R-2R ladder”, we can alter the voltage being measured by the analogue pin by diverting the current through one or more resistors by our multiple buttons. Each combination of buttons theoretically will cause a unique voltage to be measured, which we can then interpret in our Arduino sketch and make decisions based on the button(s) pressed.

First the circuit containing four buttons:

Can you see why this is called an R-2R circuit? When building your circuit – use 1% tolerance resistors – and check them with a multimeter to be sure. As always, test and experiment before committing to anything permanent.

Now to determine a method for detecting each button pressed, and also combinations. When each button is closed, the voltage applied to analogue pin zero will be different. And if two buttons are pressed at once, the voltage again will be different. Therefore the value returned by the function analogRead() will vary for each button-press combination. To determine these, I connected a numeric display to my Arduino-compatible board, then simply sent the analogRead() value to the display. You can see some of the results of this in the following video:

The analogRead() results of pressing every combination of button can be found in the following table:

After this experiment we now have the values returned by analogRead() and can use them in a switch… case function or other decision-making functions in our sketches to read button(s) and make decisions based on the user input. Unfortunately there was some overlap with the returned values and therefore in some cases not every possible combination of press will be available.

However, we’re still doing well and you can get at least eleven or twelve combinations still with only one analog input pin. You can add delay() functions in your sketch if necessary to take care of switch debouncing or do it with hardware if you feel it is necessary.

So now you have a more useful method for receiving input via buttons without wasting many digital input pins. I hope you found this article useful or at least interesting. This series of tutorials has been going for almost two years now, and may soon start to wind down – it’s time to move forward to the next series of tutorials

So if you have any suggestions for further articles (and not thinly-veiled methods of asking me to do your work for you…) – email them to john at tronixstuff dot com.

Have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column, or join our Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Breaking up an automatic room deodoriser – round two

Again we attempt to break down an automatic room deodoriser.

Updated 18/03/2013

Today we are going to tear down another automatic room deodoriser. Why?

Well the first attempt beat me, so it was time to even the score and try again with another type. The supermarket had the following units for $7.99, which seemed a little too cheap:

The “satisfaction guarantee” gave me a chuckle, the thought of writing to SC Johnson complaining that their products were not that hackable would be interesting. But would it be hackable at all? Let’s find out. The packaging promises a squirt of scent when the unit detects motion, then holds out for 30 minutes until the next release. The word motion hints that there would be a PIR inside the unit. However the instructions mention that the unit does not work that well in dark or bright rooms – which is odd, as PIRs usually work in the dark. Hmm. This unit is somewhat smaller than the previous attempt, yet still offers us a pair of alkaline AA cells:

Moving on, time to start the disassembly process. The rear shows four screws, easily removed:

revealing the fun things:

The motor drive is reduced twice, which then has a geared arm which causes the vertical motion to pressure the cylinder to release the scent. The whole mess of gears was lubricated generously, the whole lot literally came out with the touch of a finger. Removing the gears and goop reveals the motor and control boards, which clipped out easily:

Interesting – a labelled motor. Very good, what looks like to be a 3V DC motor. The control board is made up of two PCBs, a smaller module that holds a control IC of some sort, and the larger, lesser-densely populated board with the button, status LED and “motion detector”. Let’s have a close-up of that PCB:

So we have the button, which causes the motor to run; a yellow LED which blinks once every five seconds; and out motion detector in the black casing. The motion detector seemed rather familiar, so I removed the black housing around it with some pliers, which revealed this:

Huh – that looks just like an LED. The metal object inside the clear casing was even identical to what you would see inside an LED. However, foolishly I broke it off the PCB when removing the housing, so could not get any voltage to it. From reading the instructions earlier on – that mention the light/dark issue, causes me to ponder if this is some sort of light-dependent sensor?

No – it is a photodiode! However the motor looked quite worthwhile. Curious to see what is driving it, I hooked up Mr Fluke to see what happens:

No surprises there, almost three volts DC forward voltage. After applying forward current the circuit applies a quick reverse current to release, thereby causing the gears and arm to ‘squeeze’ down on the scent cylinder. So now we have a circuit board that runs on 3V, which can output 3V for a few seconds every 30 minutes – or at the press of a button.

With regards to current, another measurement was taken:

When free-running, the motor draws around 45 milliamps – and the stall current (that is, the current drawn when I force the spindle to stop) is around 675 milliamps. That is quite a strong little motor, and worth the effort. In general, this has been a good tear down, we scored some AA cells, a good motor and gears, some stink spray, and a timing circuit that could have uses elsewhere. So overall a win – the score has evened with the deodoriser world! High resolution photos available on flickr.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.