Fullscreen HTML5Med Res (??MB)HTML4

Bird song – without the mess! PCBirdies Ever wished you could have beautiful bird song in your home, without having to own a live caged bird? With PCBirdies, you can have the luxury of not one, but two singing birds. You won’t have to buy a cage or even bird seed. . . and best of all, there’s no mess to clean up! I PCBirdies is powered from a 3V hours or days without singing at all. t can be very calming and relaxing to have bird song in your home. In lithium button cell and employs two PCBirdies, on the other hand, can be fact, when people have heard this microcontrollers, each one driving its guaranteed to sing for your pleasure many times during the day, at seemproject, without knowing the techni- own piezo transducer. Arguably PCBirdies sounds similar ingly random intervals. calities, they have found it charming. Canary songs consist of a PCBirdies will sing from time series of chirps, tweets, trills to time, at random intervals so it and warbles and they seldom (they?) can pipe up unexpectedly Power: 3V from a CR2032 lithium cell repeat the same sequence twice. at any time during the day, which PCBirdies’ songs also consists of can be a pleasant diversion. You Current: 0µA when switched off, 1.8µA per IC during periods of silence chirps, tweets, trills and warbles can hear a few samples of its song 735µA per IC while chirping but its songs are much shorter, on our website. typically lasting for about eight PCBirdies is (are?) housed in Sounds: Selection 1 – typical canary sound seconds. a small plastic box. This might Selection 2 – Fife Canary PCBirdies gives the option to sound a bit cruel but it is entirely Selection 3 – various individual phrases change the canary sound from happy to be there and we can asSelection 4 – medley of the first three. one type to another. (Try doing sure concerned readers that no that with a real bird). Each sebirds were harmed or put under stress during the development of this to a canary but it we should state at the lection imitates typical canary sound project. In fact, as the proverb states, outset that a typical canary’s song is phrases. Song A is a typical canary and “A bird in the hand is worth two in more varied and they typically sing for Song B simulates a Fife canary. Song much longer periods (their songs can C is a selection that comprises varithe bush”. ous single phrases of these birds. The Inside the box are two piezo trans- last up to several minutes at a time). But then again, they may go for fourth selection comprises a medley of ducers that produce sounds which all the above played over time. simulate those of two separate birds. PCBirdies sings at random. Each So it might be said that PCBirdies is By JOHN CLARKE song is repeated between two and better than two in the hand. Specifications 28  Silicon Chip siliconchip.com.au a short interval. This has been done to avoid any clicks from the piezo transducers which would otherwise spoil the effect. Circuit details Fig.1 shows the circuit and it is quite simple, comprising two identical microcontrollers with both using same software; one microcontroller acts as master and the other behaves as the slave. Power comes from a single 3V lithium button cell. IC1 is the master microcontroller and this has an LDR connected between its GP2 and GP5 inputs, to monitor the ambient light. To do this, the GP5 output, pin 5, goes low momentarily to connect the LDR and 470kΩ resistor in series between the +3V supply and 0V, via GP5. When light is present, the LDR has a low resistance and so the GP2 input will be low; close to 0V. In darkness, the LDR’s resistance is high and GP2 will be high; close to +3V. The voltage level at GP2 is duplicated at the GP4 output which connects to the GP2 input of IC2. So when IC1 “sings”, so does IC2. But the GP4 output of IC1 is used more effectively than just following the LDR light level measurement. By taking advantage of the fact that the bird sound is not produced in darkness, the GP4 output of IC1 is also used to help IC2 resynchronise with IC1. During longer phases of no output sound from IC1, the GP4 output is taken high. This sets IC2 to sense darkness and its timer that determines the gaps between bird songs is reset. PCBirdies is fully selfcontained in a small zippy box. It will only burst into song in daylight – at night, like any good canary, he (it? they?) goes sound asleep! 27 times with a 2.4 to 17-second gap between them. There is an extended gap between each series of repeated songs and this is between 80 seconds and 9 minutes. PCBirdies only sings during daylight or under artificial light - an LDR (light dependent resistor) senses the ambient light level. The “birds” sing in and out of unison to simulate two separate birds. The two birds are re-synchronised at the end of a darkness period and also at the end of the extended gap period. Note that PCBirdies does not simply play sampled segments of real canary songs. Rather it simulates the bird song by varying the frequency, volume and length of bursts of pulse trains applied to the piezo. The volume is adjusted by changing the pulse width of signals applied to the piezo transducers. Narrow pulses give low volume while wider pulses give more volume. Maximum pulse width equates to a pulse duty cycle of 50%. Each chirp starts with a minimum pulse width, increasing to the required volume level over time. Similarly when a chirp or tweet is about to end, the pulse width is reduced to zero over S3 POWER K 1mF 10k 470k 10k MMC 3V LITHIUM BATTERY D1 1N4004 A 1 Vdd 4 MCLR/ GP3 5 GP4 3 5 GP2 2 GP5 GP0 Vss A SC Ó2013 PIEZO 1 7 2.2k 2 GP5 GP0 Vss PIEZO 2 7 2.2k 8 S1 S2 K 'PC BIRDIES' siliconchip.com.au 3 6 IC2 PIC12F675 GP1 8 1N4004 GP4 GP2 6 IC1 PIC12F675 GP1 LDR1 l 1 Vdd 4 MCLR/ GP3 Fig.1: not much to it, is there! Basically, it’s two microprocessors driving two piezo transducers. The bird songs can be altered by pressing S1 and/or S2. August 2013  29 LDR1 10k IC2 PIC 12F675 S1 1 2.2k PIEZO 1 10k CR2032 BUTTON CELL HOLDER PIEZO 2 PIEZO TRANSDUCER 1 SEIDRIB CP 2.2k 4004 470k 13140180 PCBirdies 2 1mF MMC D1 + PIEZO TRANSDUCER IC1 PIC 12F675 1 S3 S2 C 2013 Fig.2: the component overlay for the PCB with a matching photo alongside. The piezo transducers are secured to the PCB, as described in the text, and the whole assembly pops into a UB5 box. As soon as IC1’s gap timer ends, ready to play another bird song, it sets the GP4 output low and so IC2 is now also ready to begin singing. Random delay periods added between the GP4 output going low and the IC2 bird singing give the effect of the two birds singing together, sometimes but not always in synchronisation. Each microcontroller drives its piezo transducer from the GP0 and GP1 outs, pins 6 & 7 with out-of-phase 3V signals; ie, when GP0 is high, GP1 is low and when GP0 is low, GP1 is high. This results in a 6V peak-to-peak drive signal to each piezo. The 2.2kΩ resistor from the GP0 output is included for two reasons. One is to provide high frequency rolloff for the piezo signal, removing upper frequencies from the square wave drive. The rolloff is due to the 50nF capacitance of the piezo transducer combined with the series 2.2kΩ resis- tor; the result is a low pass RC filter. The 2.2kΩ resistor also prevents GP0 from being shorted to 0V when the switch (S1 for IC1 and S2 for IC2) is pressed. Normally, GP0 is set as an output but at power up, GP0 is set as an input with an internal pullup holding this input high unless the switch is pressed. Pressing the switch causes the microcontroller to change to the next bird sound available. This selection is stored in EEPROM so that the setting remains whether power is off or on. Saving power While PCBirdies is switched on, the current drain is 1.8uA per microcontroller during silence and 735µA per microcontroller while singing. Maximum current drain when both birds are singing is about 1.5mA. With the birds singing intermittently (as they do) we expect that you should get about 100 days of continuous use before the cell requires changing. At around $2 to $3 per cell, that’s a lot cheaper than bird seed! Both microcontrollers utilise a watchdog timer which is repeatedly cleared during normal program running to prevent it from timing out and resetting the micro. Typically the watchdog timer will time out after 2.3 seconds. During the gap period when there is no sound produced, the micro is in sleep mode and is woken up every 2.3 seconds by the watchdog timer (perhaps its barking wakens the napping PCBirdies?) The number of watchdog timer timeouts that occur is counted to set the gap timer period. The gap timer is reset to zero with the LDR in darkness for IC1 and with GP2 high for IC2. As already noted, power for the circuit comes from a 3V button lithium cell, type CR2032. Diode D1 is These waveforms demonstrate how the microcontroller drives the piezoelectric transducer in push-pull. In the left screen shot, the yellow trace is the output at pin 6 while the green trace is the signal at pin 7. The mauve trace at bottom is the difference between the two signals which is applied to the transducer. The resulting waveform is equal to the sum of the two waveforms (in theory) but in practice it is less. The waveforms at right were taken for the same connections as in the scope screen at left but the note is less than half the frequency and the duty cycle is also much reduced. 30  Silicon Chip siliconchip.com.au C L 9.0mm 6.5mm DIAMETER PIEZO 2 PIEZO 1 1 SEIDRIB CP 4004 13140180 PCBirdies 1 + included to provide reverse polarity protection. Normally this should not happen as the cell will only make an electrical connection to the cell holder if it is correctly inserted. However, it is not unknown for some constructors to solder cell holders in the wrong way. If that happens and a cell is inserted, the diode will conduct to protect the two microcontrollers but unless the cell is quickly removed (upon the awful realisation that it is in the wrong way) it will get hot and be quickly discharged. The lithium cell is bypassed with a 1µF capacitor. Each micro has its MCLR connected to the +3V supALL 4mm DIAMETER ply via a 10kΩ resistor. This provides a poweron reset each time power is first applied. ALL 4mm DIAMETER C 2013 Construction S3 1 2 ZO PIE ZO BATTERY HOLDER PCB (SNAPS INTO GUIDES ON SIDE OF BOX) Fig.3: this diagram shows not only how it all goes together in the box but also the positions for the switch hole (S3) and the sound holes in each end. You’ll also need a hole in the case lid above the LDR (circled in red) if you don’t use a translucent case. These waveforms show the songs being “sung” simultaneously by the two microcontrollers, with the connections being at pin 7 in each case. Note that the songs are not synchronised even though they start out in sync at switch-on. siliconchip.com.au PIE All components (including the battery and piezo transducers) for PCBirdies mount on a single PCB coded 08104131 and measuring 62 x 48mm. It is housed in a translucent blue UB5 box that measures 83 x 54 x 31mm. No screws or mounting posts are used – the completed PCB drops into the moulded rails on the side of the box, with the power switch emerging through the side. A label measuring 78 x 49mm affixes to the lid of the box. Taken at a faster sweep speed, these waveforms show how the beginning and the end of each pulse train has a much reduced duty cycle to avoid any tendency for the piezoelectric transducers to produce audible clicks, which would rather detract from the canary’s song! August 2013  31 Once the PCB is built and tested it is inserted in the box. The idea is to “slide” it in so that the power switch (S3) emerges through its hole in the box then the back of the board is pushed down so that it clicks into place in the mouldings on the case. Parts List – PCBirdies 1 PCB coded 08104131, 62 x 48mm 1 translucent blue UB5 box 83 x 54 x 31mm (see text) 1 PCB mount SPDT toggle switch (S1) (Altronics S1421 or equivalent) 2 2-pin momentary pushbutton PCB mount switches (Jaycar SP0611) 2 DIL8 IC sockets 1 PCB mount 20mm cell holder (Altronics S5056, Jaycar PH9238) 1 CR2032 lithium cell 2 piezo transducers (Altronics S6140, Jaycar AB3440) 1 LDR (Jaycar RD3480, Altronics Z1619) (LDR1) Tinned copper wire Semiconductors 2 PIC12F675-I/P microcontrollers programmed with 0810413A.hex (IC1,IC2) 1 1N4004 1A diode (D1) Capacitors 1 1µF monotlithic multilayer ceramic (MMC) Resistors (0.25W, 1% or 5%) 1 470kΩ (4-band code: yellow purple yellow brown) 2 10kΩ (4-band code: brown black orange brown) 2 2.2kΩ (4-band code: red red red brown) 32  Silicon Chip Here’s what it looks like assembled inside the box. Everything is on the one PCB. If you have used anything but the translucent blue box, you’ll need to drill a hole in the box lid so that the LDR (top, left of board) can “see” daylight. Otherwise PCBirdies will never turn on! Before installing the parts, check the PCB for any faults. Repair these as necessary. If you are building from a kit or using the PCB supplied from the SILICON CHIP shop, you will find that these PCBs are of excellent quality and so will not normally require any repairs. Follow Fig.2 for the PCB component assembly. Install the resistors and diode first. The resistors are colour coded with the resistance value. There are only three values of resistor; their colour codes are shown in the parts list. A digital multimeter should also be used to check the resistance values. Make sure the diode is installed with the correct polarity with the striped end oriented as shown in the overlay diagram. The capacitor can be installed next, along with the two push button switches and the IC sockets. Make sure the IC sockets are oriented correctly. Power switch S3 is mounted harddown on the PCB and its main body terminal is soldered to the PCB before the remaining three switch pins are soldered. The 20mm button cell holder can be installed taking care to orient this as shown. If you are using a translucent case, then the LDR can be mounted at about 5mm above the PCB. That way the LDR will receive light through the box sides (even if a panel label is attached to the lid). If a grey or black case is used, the the LDR top face needs to be 14.5mm above the top of the PCB so that it can be inserted into a hole drilled in the lid of the case. Insert the 3V cell into its holder and check that there is a 3V supply between pins 8 and 1 of each IC socket when switch S3 is turned on. If this is correct, turn the power switch off and mount the ICs. The piezo transducers are mounted at about a 45° angle on the side of the PCB, sitting within the cut outs. Fig.3 shows the arrangement. We soldered the transducer wires directly into the signal output pads after first looping the wires through the two holes that provide for stress relief. The piezo transducers have two flanges for mounting and we looped some tinned copper wire through the flanges and soldered these to the pads on the PCB. This keeps the transducers in position with one flange on the top side of the PCB and the other flange on the bottom of the PCB. The PCB is designed to clip into the integral side rails of the box. A 5mm hole is required in the side of the box for switch S3. The diagram shows where the hole should be. If you must use a grey or black case, drill a suitable hole for the LDR in the lid, immediately above where the LDR is mounted. An array of holes is also required in the ends of the box. Use the photos and diagrams for the positioning of the holes and drill these out to 4mm in diameter. The front panel can be downloaded siliconchip.com.au Before placing the PCB in the box, you’ll need to carefully drill sound holes in each end. If you don’t do this there will be two very muffled canaries! The exact positions are not important but you should aim to make the pattern symmetrical about the centre so it looks good! from the SILICON CHIP website (www. siliconchip.com.au/shop and then select “Panel artwork”). It’s a free download for subscribers (print or online) but there is a nominal charge for non-subscribers. Print the label onto good quality thick paper – photo paper is ideal. It can be secured to the lid with a suitable glue or Silicone. The hole for the LDR (required in a solid coloured box only) can be cut out with a sharp craft knife or leather punch. Changing the songs When PCBirdies is first turned on, the bird sound produced by both IC1 and IC2 are of the Fife Canary. Changing the bird sound produced by IC1 is done by pressing S1 during power up. Similarly, changing the bird sound If you don’t get any sound from PCBirdies after final assembly (and it worked before you put the PCB in the box, make sure that the CR-2032 button cell is right down in its holder. Push it down so that it clicks into place to ensure reliable contact. produced by IC2 is done by pressing S2 during power up. Power up involves switching off S3 for a few seconds then switching it on again. The pressed switch (S1 and/or S2) is released after five seconds from power up. You can either press S1 on its own, S2 on its own or both switches during power up to change the song(s). If just S1 is pressed and held during power up, then only the song produced by IC1 will change; similarly if just S2 is pressed, it’s only the song produced by IC2 that changes. With both switches pressed, songs from both IC1 and IC2 will change. There are four bird song selections. The Fife Canary bird song is the first that is set in the program. The next selection is a different canary bird song. The third and fourth selections are medleys of the bird songs. The third selection provides just a few of the more distinctive phrases used within the Fife and second canary songs. These are played at random. The fourth selection provides a medley of both the full Fife Canary repertoire, the full second canary song repertoire plus the phrases available from the third selection. These are all played at random. You will return to the original Fife Canary sound with the next selection accessed by S1 and S2 at power up. If you want to have both IC1 and IC2 play the same repertoire, then press just one of the switches (S1 or S2) as many times as necessary during power up until that IC plays the same song as the other. SC Full range of PICAXE products in stock now! PICAXE Chips, Starter Packs, Project Boards, Experimenter Kits, Books, Software and Accessories. PICAXE 2x16 and 4x20 OLED Displays OLED displays provide much brighter displays, better viewing angles and lower current consumption making them a great alternative to LCD’s. PICAXE Starter Packs available for 08M2, 14M2, 18M2, 20M2, 28X2 and 40X2 Microprocessors. This module allows PICAXE projects to display (yellow on black) text interfacing via one single serial line or I²C bus. PICAXE-18M2 chip is provided pre-programmed with the open-source AXE133 firmware. For pricing and to shop online, visit www.wiltronics.com.au Ph: (03) 5334 2513 | Email: sales<at>wiltronics.com.au siliconchip.com.au August 2013  33