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Does that <at>!#$%*~ dog drive you Barking Mad? Don’t get mad – get even with our new By JOHN CLARKE BARKING DOG Let’s face it: there are few things more annoying than a dog which won’t shut up. But now you can fight back: every time it starts to bark, give it a blast of ultrasonic screaming. It won’t hurt the dog but it should quickly learn that barking can have unpleasant results! Barking dogs can make life a misery, especially at night when you are trying to get to sleep. Or maybe you are not trying to sleep; you just want some peace and quiet! Of all the tensions that can arise from living in suburbia, barking dogs must be right there near the top of the list. If you have this problem, you have our sympathy. But we have something better and more effective than sympathy – our Barking Dog Blaster, or BDB. It won’t hurt the dog but use the BDB judi30  Silicon Chip ciously and it should teach the dog to moderate its barking. Now we’re not being too optimistic here. The BDB won’t solve the problem in all situations and we should men- Features c sound bursts • High volume ultrasoni • Adjustable timer ncy • Adjustable output freque tor ica ind un y/r ndb • LED sta • Audible test current • Low standby quiescent tion some of them. For example, it won’t work if the dog is old and deaf or too far away. So if the offending creature is several doors down the street, it is not going to work. It should work with dogs in adjacent properties but beyond that, forget it. Some dogs are just stupid or very aggressive and again, the BDB is probably not going to work in those situations. And nor will any barking dog deterrent completely siliconchip.com.au Above is the Barking Dog Blaster driver while the 4-tweeter business end is at right. stop barking; it is impossible to stop a dog from barking all the time, particularly if someone enters the property where they live. Having said all that, the BDB can work well in many situations, particularly if the dog is within a distance of about 20m or thereabouts. We are pretty confident in making this statement as we have published similar ultrasonic projects to know that they do work to help stop a dog barking. Two projects designed by SILICON CHIP (called Woofer Stoppers) were published in May 1993 and February 1996 and two projects, developed by Oatley Electronics (called Shut that Mutt) were published in July 1999 and April 2004. The BDB works, provided you use it sensibly. Each time the dog starts barking, you need to give it a burst of ultrasonic noise. It needs to associate the unpleasantness of the ultrasound occurring each time it barks. Now we know that commercial ultrasonic barking deterrents are available in some pet shops but they use a single tweeter to produce the ultrasonic energy. That’s OK but our BDB is a much higher power device, employing four tweeters arranged as a “line source array” similar to a high-power PA speaker. The line source produces a narrower ultrasonic beam than a single tweeter and it can be aimed at the source to produce the maximum effect. We need to do that in order for the dog to perceive the ultrasound as being loud. Scope 1: green and blue traces show the alternate 5V pulses at the Mosfet gates. The Mosfets then drive the transformer (T1) in push-pull fashion and the filtered output of its secondary (yellow trace) appears across the tweeters. siliconchip.com.au Scope 2: captured with a longer time base, this shows one entire burst being delivered to the tweeters. Burst duration is around 10ms. The ramp up and ramp down at either end minimise audible clicks from the tweeters during operation. September 2012  31 Scope 3: a series of pulses, showing the repetition rate of about 100ms. They start when the button is pressed and continue for the selected duration of 1-50s, or until it is pressed again. While dogs can hear ultrasonic frequencies, they need between 10 and 20dB more sound level to perceive the 25kHz to 30kHz frequency range at the same sound level compared to dogs’ most sensitive frequency of 8kHz. (See www.lsu.edu/deafness/ Hear-ingRange.html). In addition, the tweeters of the BDB are pulsed on and off rather than being driven at a constant level. This allows them to be driven at a much higher level without the risk of being burnt out. How will you know if the BDB is working, since humans cannot hear beyond 20kHz? We have provided an audible test mode whereby the BDB is driven at 1.5kHz but at considerably reduced level – so you won’t be deafened. And when the BDB is working normally, you will hear a faint clicking, although you need to be reasonably close to it; within a few metres. As can be seen in the photos, the BDB comes in two parts: the driver unit which is housed in a small plastic case and the line source tweeter array. The driver unit can be power from a 12V DC plugpack or a 12V battery. In standby mode it typically draws 106 microamps – so battery operation is quite feasible. The driver unit has a LED which flashes when the unit is in standby mode and it lights continuously when the BDB is doing its stuff. Other animals? There are many animals that have much better high-frequency hearing 32  Silicon Chip Scope 4: voltage across the tweeters when operating in audible (test) mode. The frequency is around 2kHz while the duty cycle is extremely low; this time to avoid bursting your eardrums! than humans. In the past, many readers – particularly those in the bush – have asked “would this work with kangaroos”? “What if I mounted one on the front of the ute, would it scare them off the road?” Now we’re no experts on these marsupials (except some say something about a few ’roos loose in the top paddock) so we can’t really say yea or nay – but if you’re troubled by Skippy, it could perhaps be worth a try. But then again, our (admittedly limited) experience is that blasting ’roos with your car horn has little or no effect – they either keep hopping on their chosen path or just stand there staring at you – so maybe a blast of ultrasonics will have exactly the same effect. One thing, though: the tweeter array is almost certainly not weatherproof so it couldn’t be a permanent installation on the bull bar! Circuit operation The circuit for the BDB is shown in Fig.1 and is based on a PIC12F675 8-pin microcontroller, IC1. This is used to drive two Mosfets, Q1 & Q2 and these in turn drive transformer T1. The transformer output drives the piezo tweeters via a series resistor and parallel inductor. IC1 also drives the standby/run LED, powers trimpot VR1 and monitors the start switch. IC1 is normally in “sleep” mode, drawing only about 100µA. It’s woken from this mode by pressing the start switch – this discharges the 10µF capacitor connected to its GP2 input (pin 5) via a 100Ω current-limiting resistor so this input is pulled low. IC1 first sets the GP5 output (pin 2) high to drive LED1, via a 560Ω resistor. This also pulls the top of VR1 high. It then acts as a voltage divider across the 5V supply. The voltage at VR1’s wiper is monitored by input AN3 (pin 3) and is converted to a digital value by IC1. This sets the timer period. A low voltage at AN3 provides a short timer period while a higher voltage provides a longer timeout period. Incidentally, VR1 is also used to adjust the output frequency, as we shall see later. The trimpot is connected to GP5 (rather than directly to the 5V supply) to reduce the current drawn during standby to just under 2µA. Permanent connection would result in a 500µA continuous drain. Under the control of its pre-loaded firmware, IC1 now drives the two Mosfets from its GP1 and GP0 outputs (pins 6 and 7) at a rate that varies between 25kHz and 30kHz. There is a dead time between when the gate of one Mosfet is driven off (to 0V), to when the second Mosfet is driven with a 5V gate voltage. The dead time prevents one Mosfet from switching on before the other has switched fully off, preventing momentary short circuit currents. Gate drive to each Mosfet is via a 10Ω resistor to prevent oscillation at the threshold of switch on. The 5.1V zener diodes clamp any voltage produced at the gate due to capacitance between the drain and gate. The 10kΩ siliconchip.com.au siliconchip.com.au D G D S Q1, Q2 A ZD2 5.1V 1W K 10k 7 GP0 Vss 8 AN3/GP4 VR1 10k IN GND A SC  2012 K  LED1 A BARKING DOG BLASTER 100nF 3 GP5 2 TIMER 560 (CON1) START S2 (CON1) – + 12V POWER OUTPUT Fig.1: the circuit is based on a PIC12F675, a pair of Mosfets, a transformer . . . and not much else! G 10 IC1 PIC12F675 -I/P 10F 16V 100 2.2k * – CON2 K K A S 1N4004 K Q2 STP30NE06L OR RFP30N06LE D A 10k GP1 1k 10F 16V D1 1N4004 A GP2 Vdd MCLR 5 1 4 6 100nF GND 1k 10F 16V +5V OUT K IN REG1 LP2950ACZ-5.0 * USE EITHER POWER SWITCH OR LINK (CON1) OUT LP2950ACZ-5.0 ZD1, ZD2 8T 8T S G ZD1 5.1V 1W K 10 F1 2A FUSE1 2A POWER SWITCH* + 12V DC INPUT A 20T CON3 LED 4 x PIEZO TWEETERS COMPONENTS WITHIN DOTTED LINE MOUNTED IN SPEAKER BOX + + + L1 47 5W T1 ETD29 Q1 STP30NE06L OR RFP30N06LE LOW ESR LOW ESR D 2200F 16V 2200F 16V Saving power Power for the circuit is from a 12V supply. Two 2200µF low-ESR capacitors bypass the supply rail. A 12V output is also included to power a UHF remote switch receiver (we’ll look at this next month). A 5V supply for IC1 is derived from the 12V supply (via reverse polarity protection diode D1) by means of a low quiescent current regulator, REG1. Input and output terminals of REG1 are bypassed with 10µF capacitors and IC1 is further directly bypassed with a 100nF capacitor. The quiescent current drawn by REG1 is typically only 75µA. IC1 is normally in sleep mode where it is drawing around 10µA. It is woken by a watchdog timer periodically at approximately 0.5s intervals so that it can flash the LED momentarily. The standby LED (LED1) is flashed at a low duty cycle so the 5.4mA normally used to drive the LED is reduced to an average of 21µA. Overall current drain from the circuit is typically 106µA and this low power allows the BDB to be connected to a 12V battery without causing any noticeable discharge over time. When driving the piezo tweeters, the BDB obviously draws more current – an average of around 350mA peak per piezo tweeter during the pulsing period. When using four tweeters, the + 350mA peak per piezo tweeter 25kHz to 30kHz sweep in 20 steps 10ms every 100ms 40Vpeak-to-peak 1 second to 50 seconds adjustable 1.5kHz tone at 3% duty Momentary flash each half second during standby; continuously lit during ultrasonic driving. Alternate flashing in test mode. 12V at 1.5A 180µA maximum, 105µA typical Supply voltage: Quiescent current drain: Current drain when driving piezo tweeters: Frequency range: Ultrasonic burst: Drive voltage: Timeout: Low frequency test: LED indicator: Specifications pulldown resistors are included to ensure the Mosfets are held off before the GP1 and GP0 outputs are set to low outputs in the IC1 program. Mosfets Q1 and Q2 drive the transformer in push-pull mode with one primary winding driven and then the other primary winding driven in an alternate fashion. This produces an AC waveform at the transformer secondary. The AC waveform is a square wave and is not an ideal wave shape to drive the piezo transducers. The sharp rise times of the waveform would produce audible clicks from the transducers. So the square wave is filtered using a resonant circuit comprising a 200µH inductor and the 220nF total capacitance across the four piezo transducers. The resonance occurs at 24kHz and the 47Ω resistor isolates the low impedance drive of the transformer from the resonant circuit. The result of this filtering is a relatively clean sine wave over the 25 to 30kHz frequency range. September 2012  33 12V IN CON2 10 S1 F2 5.1V 100nF VR1 10k LED1 2X STP30NE06L BARKING GOD GNIKDOG RAB RBLASTER ETSALB 125108121 2180152 T1 CON3 TO PIEZO TWEETERS S3 S2 SPEAKER OUTPUT F1 F3 5.1V 1k 10 10k 560 IC1 PIC12F675 1k 10k A 10F ZD2 Q2 2.2k 100 +12V OUT 0V LP2950ACZ-5.0 REG1 10F 10F 4004 D1 100nF S2 START SWITCH 2200F 16V LOW ESR CON1 START +12V OUT 0V 2200F 16V LOW ESR F1 2A POWER SWITCH TO S1 (WIRE LINK IF S1 NOT USED) C 2012 ZD1 Q1 ETD29 Fig.2: assembling the driver PCB shouldn’t take you long – even the transformer is not too difficult to wind. The board is designed to fit into a UB3 Zippy box without the need for screws to hold it in place – athough there’s space for mounting screws just in case you want to mount it somewhere else. current rises to 1.4A. Total current drain depends upon how often and for how long the piezo tweeters are driven. Because of the intermittent use of the BDB, this is still within the capabilities of most 12V batteries but if you use it often and have the time-out timer set towards the maximum end of the range (50s), the battery might not last too long at all. Obviously, this circuit is NOT recommended for continuous operation – not only because the battery won’t like it but the tweeters will also get a bit hot under the collar as well. It also somewhat defeats the whole purpose! Some readers may wonder why we didn’t use a microphone to trigger the circuit, as we have done in the past. The reason is quite simple – unless operating pretty close-by with gain down low, the circuit tended to trigger with every passing car, low-flying plane, loud voice, cat meow, ball bounce . . . you get the picture! piezo tweeter array. We’ll start with the driver electronics. With the exception of the four tweeters, inductor L1 and one 5W resistor, all components for the BDB are soldered onto a PCB coded 25108121, measuring 106 x 61mm. It is designed to clip into the integral side pillars of a UB3 box. The overlay diagram is shown in Fig.2. Begin by checking the PCB for breaks in the tracks or shorts between them. Check also that the hole sizes are correct for each component to fit neatly. The screw terminal holes and transformer pin holes are 1.25mm, while larger holes again are used for the fuse clips. Assembly details Begin by installing the resistors, followed by the diodes. Table 1 shows the resistor colour codes but you should also check each resistor using a Digital Multimeter. Note that there are two different diode types: 1N4004 for D1 and 5.1V zener diodes for ZD1 and ZD2. The resistors are not polarised but the diodes certainly are! IC1 is mounted on a DIL8 socket. Install this socket now, taking care to orientate it correctly. Leave IC1 out for the time being though. Fuse clips for F1 are installed next. While fuses are of course not polarised, the fuse clips have an end stop to prevent the fuse from sliding out. So the clips must be oriented correctly and to ensure this, it’s best to clip the fuse into the two clips first (with the end stops to the outside of the fuse) so that it holds the fuse in between the two clips. Then insert the clips into As mentioned earlier, the project is in two parts – the driver electronics and the The assembled PCB ready for connection to power and the “start” switch (via the 6-way terminal block at left) and the tweeter box (via the 2-way terminal block at right). Everything else is on the PCB. Provision is made for a power switch but we really don’t think one is necessary – if you don’t connect a power switch, wire a link between the top two terminals in the 6-way block. 34  Silicon Chip siliconchip.com.au the PCB and solder them in place. A 6-way screw connector for CON1 is made using three 2-way connectors that are clipped together by sliding the dovetail mouldings on the sides of the terminals together. When mounting, make sure the screw terminals are oriented with the opening toward the outside edge of the PCB. CON3 comprises just a single 2-way screw terminal. Q1 and Q2 mount vertically with the top of each tab 24mm above the top of the PCB. LED1 is mounted with its top 30mm above the PCB (its anode (A) has the longer lead). The capacitors can then go in, followed by trimpot, VR1. Make sure that the electrolytic capacitors are oriented correctly. Transformer details It’s unlikely that you will find a transformer wound to our specifications so you’re going to have to wind it yourself. It’s not hard to do – Fig.3 shows the transformer winding details. The primary winding uses eight turns of figure-8 20 x 0.18mm wire, wound in two layers of four turns each. The secondary uses 0.8mm enamelled copper wire wound in one layer of 20 turns. The secondary winding is done first. To do this, first strip say 10mm of the enamel from one end of the 0.8mm enamelled copper wire using some fine emery paper or a hobby knife to 20 TURNS F3 Resistors (0.25W, 1%) 2 10kΩ 1 2.2kΩ 2 1kΩ 1 560Ω 1 47Ω 5W 1 10kΩ mini horizontal mount trimpot (VR1) 1 100Ω 2 10Ω 1.3m length of 90 x 12mm DAR pine (+ extra 356mm for rear backing panel if used) 16 No.6 x 15mm round head screws or similar 1 length of 20 x 0.18mm figure-8 wire (length as required) 1 cable gland (if required – see text. Alternative is mono 6.35mm socket and plug). 1 bracket for cable gland or socket (see text) 9 10 11 2 12 1 13 S1 (STRIPED) 4 TURNS EACH LAYER 7 F2 5 8 4 9 3 11 S2 F1 (STRIPED) 2 1 Capacitors 2 2200µF 16V low ESR electrolytic capacitors 3 10µF 16V electrolytic capacitors 2 100nF MKT polyester Speaker box 8 3 S3 6 Semiconductors 1 PIC12F675-I/P microcontroller programmed with 2510812B.HEX (IC1) 1 LP2950ACZ-5.0 low quiescent current 5V regulator (REG1) 2 STP30NE06L or RFP30N06LE logic-level Mosfets (Q1,Q2) 1 1N4004 diode (D1) 2 5.1V 1W zener diodes (ZD1,ZD2) 1 high-brightness 3mm LED (LED1) 7 6 5 4 Parts List – Barking Dog Blaster 1 PCB coded 25108121, 106 x 61mm 1 UB3 box 130 x 68 x 44mm 4 piezo tweeters (Motorola/CTS KSN1005A or equivalent) (or Jaycar CT-1930) 1 ETD29 transformer (13-pin former and N97 cores) (T1) (element14 cat 1422746 for the former and 1422745 for the cores (2 required) 1 200mm cable tie to secure the transformer cores 1 28 x 14 x 11mm powdered iron toroid (Jaycar LO-1244) (L1) 2 M205 fuse clips 1 2A M205 fast blow fuse (F1) 4 2-way PCB mount screw connectors with 5.08mm pin spacings (CON1,CON3) 1 SPST momentary push button switch (Jaycar SP0700, Altronics S1084) (S1) 1 SPDT or SPST toggle switch (S2) (optional) 1 PCB mount DC connector (CON2) 1 DIL8 IC socket 1 cable gland for 3-6mm cable 1 1.2m length of 0.5m enamelled copper wire 1 1.2m length of 0.8mm enamelled copper wire 1 600mm length of 20 x 0.18mm figure-8 wire 1 60mm length of medium-duty hookup wire 4 TURNS EACH LAYER 13 Fig.3: transformer winding detail. siliconchip.com.au scrape it off. Pre-tin the wire end, wrap it around pin 4 on the underside of the transformer bobbin and solder it close to the bobbin. Now wind on 20 turns side-by-side. The direction of winding (whether clockwise or anticlockwise) doesn’t matter. Cover this winding layer with a single layer of plastic insulation tape. Now run the wire down perpendicular to these windings and terminate the wire onto terminal 3 and cover this perpendicular length with a layer of insulation tape. The primary winding, made from the figure-8 cable, is first stripped of 10mm of insulation at one end and the two wires are soldered to pins 7 & 9 of the bobbin, with the polarity stripe to pin 7. Now wind on four turns making sure the wire lies flat without twists, so that the striped wire stays to the right. The four turns should fully fill the bobbin and the next four turns will be on the next layer (there’s no need for insulation tape between them). Terminate the polarity striped wire end onto pin 11 and the other wire to pin 7. Once wound, slide the cores into the former and secure with either a 200mm long cable tie or with clips. These clips push onto the core ends September 2012  35 Here’s how the driver PCB fits inside the UB3 box. No screws are required because the board is made to snap into the cutouts in the side guides. The two leads shown in the terminal block on the left go to the “start” switch on the front panel; no wiring is shown here for the on/ off switch, should you decide to fit one. If you don’t, a wire link should be connected between the top two terminals of the group. and clip into lugs on the side of the bobbin. The transformer can now be installed on the PCB. Note that its primary side has seven pins and the secondary side has six pins, so it can only go in one way. That completes the PCB assembly. Front panel The front panel label can be downloaded as a PDF file from our website. You can print it out onto paper or clear overhead projector film. Now mark out and drill the holes in the lid of the case for switch S2 (and S1 if used) and for the LED. For longest life, we laminate the label using an office laminator (they are ridiculously cheap these days!). The label can be attached to the lid with spray adhesive, double-sided tape or silicone sealant. If you use double-sided tape be very careful when placing the label as you only get one shot at it! The hole for switch S1 is cut out of the panel label using a sharp hobby knife or leather punch. Its position is shown on the panel artwork. A hole is required along one side of the box for the power plug entry and another at the end of the box for the cable gland for the lead connection to the piezo tweeters. If the power switch is not required, bridge the two power switch terminals with a short length of tinned copper wire. Wire the start switch using the hookup wire by soldering wires to the switch terminals and terminating into the start switch terminals. Fig.2 shows the details. Speaker box A box for the four in-line piezo tweeters can be made using 90 x 12mm DAR (dressed all round) radiata pine timber. The diagram in Fig.4 shows the dimensions. Note that we used 19mm timber ‘cause that’s what we had, but we then needed to cut away some of the sides inside the box so the tweeters would fit. Using 12mm timber will allow the tweeters to fit without any doctoring of the timber. The 76mm holes are cut out using a hole saw or a jig saw. The timber is cut to size and Resistor Colour Codes o o o o o o No. 2 1 2 1 1 2 36  Silicon Chip Value 10kΩ 2.2kΩ 1kΩ 560Ω 100Ω 10Ω 4-Band Code (1%) brown black orange brown red red red brown brown black red brown green blue brown brown brown black brown brown brown black black brown glued together with PVA glue. Weatherproofing the box will be necessary if it cannot be installed under cover. Additionally, a weather proof box will need a back panel on the box and the whole box painted. The backing can be 356 x 66 x 12mm to fit flush inside the back hole of the box or 380 x 90 x 12mm and mounted on the back, adding 12mm to the speaker box depth. The piezo tweeters are secured with the No.6 x 15mm round head screws. Countersunk screws could be used instead, provided they are not made too tight as they can otherwise crack the plastic around the hole of the piezo tweeter casing. For weatherproofing, seal the mounting of the tweeter against the timber, preferably with speaker sealant. If you use silicone sealant, this will make removal of the tweeters difficult unless you first coat the back of the tweeters with some mineral oil to stop Capacitor Codes Value µF Value IEC Code EIA Code 100nF 0.1µF 100n 104 5-Band Code (1%) brown black black red brown red red black brown brown brown black black brown brown green blue black black brown brown black black black brown brown black black gold brown siliconchip.com.au 380 SIDE 66 47.5 90 95 95 47.5 95 BOTTOM TOP SIDE CL 90 76mm DIAM. 76mm DIAM. 76mm DIAM. 76mm DIAM. 380 FRONT: 380 x 90 x 12mm SIDES: 380 x 90 x 12mm TOP & BOTTOM: 66 x 90 x 12mm ALL DIMENSIONS IN MILLIMETRES REAR BACKING (WEATHERPROOF VERSION): 356 x 66 x 12mm And here’s the business end of the unit, with the photo above and Fig.4 above that. The four tweeters are shown from the rear. Inset at left is a close-up of the inductor (L1) simply connected across one of the tweeters (which are all in parallel). The 47Ω 5W resistor connects in series with one of the leads coming from the driver. This shot shows another cable gland to keep the cable captive; if you want to make the speaker box detachable, you could use a 6.35mm socket and plug instead. While these photos show the box horizontal for convenience, in fact it should be used vertical to achieve the desired “beam” effect. the silicone adhering to the plastic. Before wiring the piezo transducers, inductor L1 should be wound. This has 39 turns of 0.5mm enamelled copper wire on a 28 x 14 x 11mm powdered iron core. The tweeters are wired up in parallel (with all plus terminals wired together and all minus terminals wired together). The inductor is simply soldered between the + and – terminals of one of the tweeters (ie, in parallel). You’ll need to scrape off a little of the wire insulation to allow it to be soldered A 47Ω 5W series resistor connects between the + terminals of the tweeters and one of the incoming wires from the driver unit. The other wire goes direct to the negative tweeter terminals. siliconchip.com.au The external connection wire will need to be clamped to the box. For cable anchoring, you can use a cable gland attached to a suitable bracket screwed to the timber. Alternatively, if a rear panel is used, the cable gland can be mounted into this. Or you could use a suitable plug and socket (eg, a 6.35mm mono) to allow the tweeter box to be disconnected from the driver unit. Testing Before going further, remove fuse F1 and check that IC1 has NOT been fitted to its socket. Apply power and check there is between 4.94V and 5.06V across pins 1 and 8 of the IC1 socket. If the voltage is outside this range, check for short circuits or open circuit solder connections or incorrectly placed or oriented components. If the voltage is OK, then switch off power and insert the fuse and IC1 making sure that IC1 is oriented correctly. Adjust VR1 to mid position (for a 25 second timer). Connect the piezo tweeters to the BDB. Press and hold the start switch and connect power. The LED should flash on and off at about three times per second. When the switch is released, the LED should begin flashing at a one second rate. Pressing the switch should start the BDB and the piezo should sound continuously at 1.5kHz (ie, well within your hearing range) at a relatively low volume. This is the test tone and the LED should flash three times per second. The test tone will continue until the timer has timed out or the start switch is pressed. The BDB then automatically reverts to the normal ultrasonic sound delivery. Now the LED will briefly flash once every half second. September 2012  37 90 POWER 12V DC + ILICON S CHIP START g o D g n Barki STANDBY/RUN Fig.5: you can photocopy this label and glue it to the front panel or you can download it and print it out from siliconchip.com.au The ultrasonic tone is started with the start switch and will either time out or it can be stopped by pressing the start switch again. To return to the audible test tone, power must be switched off/disconnected for several seconds so the voltage on IC1 dies away to 0V. Press and hold the start switch and apply power to obtain the test frequency as described before. Training the barking dog When used to train the barking dog, the timer duration should be set to a length sufficient to stop the dog barking but ideally should not run longer than the barking duration. Timer settings are from 1s when the trimpot is set fully anticlockwise to 50s when set fully clockwise. The timer can be stopped immediately while running by pressing the start switch. Mounting the tweeter box The tweeter box should be located as close as reasonably possible to where the troublesome pooch resides (although this may sometimes be difficult!). It operates best when it is used vertically although you can use it horizontally at short range if space is not available. The box can be mounted with suitable brackets onto a tree trunk, under the eaves of the house or on a fence post as appropriate. Make sure the speakers are facing in the direction of the dog. It’s best if the box is tilted downward slightly, aimed to cover the entire barking dog area. Best orientation for sound coverage can be determined using the test frequency (if that is practical). Adjusting the frequency What if Yap-yap doesn’t seem to show any reaction to your attempts to shut him up? Perhaps the BDB is putting out a frequency that he doesn’t find too disturbing so doesn’t react to it. So we’ve made provision to alter it to a frequency he will not like so much . . . hopefully! This is done with a combination of the start switch and VR1. With this adjustment, the frequency can be altered by up to 10kHz. The procedure is to hold down the start switch for eight seconds. Note that this is different to the procedure to obtain the humanaudible tone where the power must be switched off and then on with the start switch pressed. For the frequency adjustment, the power is left on. After the eight seconds, the piezo transducers will now be driven with bursts that can be adjusted in frequency by the trimpot (VR1). Fully anticlockwise, VR1 will set the frequency to below 20kHz and fully clockwise, the frequency will be set for above 30kHz. The adjustment can be made for the lowest frequency that is inaudible. The BDB will continue cycling bursts of signal every few seconds so long as the start switch is kept pressed. Frequency will change with changes to the trimpot VR1 position. When the switch is released, the bursts will stop and the revised frequency for the bursts will be stored in EEPROM and this is the new BDB frequency unless changed again through this adjustment SC procedure. Next Month: We’ll show you how simple it is to go wireless! We’ll add our UHF remote switch (SILICON CHIP January 2009) to the Barking Dog Blaster so that you can keep the “start” switch in your pocket, giving you almost instant retaliation when Fido gets you barking mad . . . Australia’s BEST VALUE Test Equipment Agilent DMMs Wide-Screen DSOs Bench Power Supplies with USB and Digital Filter, 30V, 5A from from $98.95* $329.00* from $87.95* 4-in-1 Test Station with PSU, Counter, DMM, Function Generator from $874.50* *Prices above include GST. Freight Extra. Callers welcome at our Castle Hill, NSW store. Stock subject to prior sale. Phone for availability. SPECIAL OFFER! Mention SILICON CHIP when placing any order over $200 and get a FREE set of Test Leads worth $24.95 +gst! OFFER OPEN UNTIL 31 DEC 2012 38  Silicon Chip Sydney Melbourne Adelaide Brisbane TRIO SmartCal gives you the best value-for-money in test equipment. Visit our website www.triosmartcal.com.au and grab a bargain. Or call 1300 853 407 now! siliconchip.com.au