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Speedometer Head-Up Displays By LEO SIMPSON This readout from the OBDII-based head-up display shows the speed, RPM (bargraph) and fuel consumption. The fuel reading here is just 1.8l/100km, achieved while coasting on a trailing throttle in gear. What’s available, the options & the pros & cons There is no need to buy the latest Commodore or an up-market European car in order to get a head-up digital display of your speedometer. For around $100 or less, you can purchase an OBD or GPS head-up display (HUD) which is easy to read and has the bonus of being far more accurate than your vehicle’s own speedometer. I HAVE SEEN the light and it is good. It is the digital image of my vehicle’s speed, floating somewhere in front of my windscreen. I no longer have to avert my gaze from the road ahead to check my speed: something I need to do frequently to avoid the risk of being booked in Sydney’s manifold speed zones. Of course, while I want to avoid speed fines I also want to travel as fast as is legally possible in any speed zone. After all, why dawdle when you can dash? So if traffic and road condi- This GPS head-up display was purchased on eBay for around $100 and can be powered via the supplied cable from either a USB interface (ie, in the car) or a 12V accessory socket. 14  Silicon Chip tions permit, I like to travel close to the legal speed limit. Trouble is, if you rely on your car’s speedometer, you will almost always be travelling more slowly than you need to. Why is that? Because under Australian Design Rules, modern car speedometers must never indicate more than the actual speed. But they can indicate the actual speed optimistically by a factor of 10% more plus 4km/h. So at an actual speed of 60km/h, the indicated speed could ostensibly be anywhere from 60km/h to 70km/h. Similarly, at 80km/h, the indicated speed could be anywhere from 80km/h to 92km/h and at 110km/h (the maximum legal speed in most states), the indicated speed can be anywhere up to 125km/h. In practice, car speedometers are rarely so wildly optimistic but on my own 2004 Honda Accord, an actual speed of 100km/h gives an indicated reading of 107-108km/h. In these days of fancy car electronics, this really siliconchip.com.au The GPS head-up display in action. A piece of film attached to the windscreen reflects the speed readout on the LED displays. The reading here is 44km/h but note that the car’s speedo shows more than this because (a) it’s slightly optimistic (ie, reads higher than the true speed) and (b) because the angle of the photo has introduced some parallax error. does seem silly, especially as odometers are typically much more accurate and appear to be within ±1% or 2%. Of course, none of this is news to anyone who uses satellite navigation in their car. You can read your actual speed, along with a lot of other navigational information on the display. Many, if not most, smart phones now on sale also have in-built satellite navigation so there is no need to rely on your car’s speedo when setting your cruise control; just run the car up to the legal speed as indicated on your GPS and hit the button to set the cruise control. Most other drivers on expressways now seem to do the same thing, as do long-distance truck drivers. The problem with the speed reading on most GPS units, such as those made by Garmin, Tom-Tom and Navman etc, is that it is too tiny. You cannot just glance at it to see the speed. And while you’re peering at the GPS, your attention is diverted from the road and when you look back up, you might be veering off into the incoming traffic! In the meantime, your passenger is liable to be seriously terrified! Even if you do have GPS satellite navigation in your car, a GPS head-up speed display is even better. So resiliconchip.com.au cently, I purchased one from eBay but I have since discovered a local source advertising another GPS head-up display in the NRMA publication, the “Open Road” – see http://mypolaris. com.au/hud/indexflash.html Both work on the same principle. Option 1: GPS HUD In essence, the GPS head-up display I purchased consists of a small plastic case with three green LED 7-segment displays. The unit is installed forward of the speedo binnacle on the dashboard and tilted up so that the reflected display is within your field of vision but not so high as to be distracting when you are looking at the road ahead. The LED displays are arranged back to front and reversed in order so that the reflection reads correctly. The unit is powered from the car’s cigarette lighter and that is a drawback because inevitably you have a long cable from the closest cigarette lighter or accessory socket to the unit up on the dash. The same comment applies to any after-market GPS sat-nav unit made by Tom-Tom, Garmin etc (unless you operate it from the internal battery). To improve the reflectivity of the windscreen, a small piece of dark plastic is arranged to improve the contrast of the display. However, it is quite difficult to install it in precisely the right place in order for the reflected reading to be centred in the display. In my case, this is because it is a long way from my eyes to the plastic piece on the windscreen, about one metre, and my arms are simply not long enough to be able to carefully position the plastic piece while viewing it from the normal driving position. The unit incorporates an LDR (lightdependent resistor) to sense ambient light levels and reduce the display brightness for night-time driving. Display visibility is quite adequate for driving at night and in overcast conditions but suffers somewhat in bright sunlight and especially if you are wearing polarised sunglasses. In use, the display appears to update as often as about five times a second, depending on whether the car is accelerating or slowing down. How accurate is it? We don’t really know but we think that it is within ±1% + 1 digit. In practice, when you are maintaining a constant speed on a flat section of road, the reading fluctuates only very September 2013  15 The iFOUND head-up display unit is available for around $75 and is supplied with a cable which plugs into the vehicle’s OBDII socket. As well as speed, RPM and fuel consumption, it also has the option of displaying coolant temperature or battery voltage (instead of the speed) at the touch of a button. Option 2: OBDII HUD The readout on the dash-mounted head-up display unit is a mirror image so that is reads correctly when reflected off the darkened film attached to the windscreen (note: this unit is also shown updside down). slightly, say from 99km/h to 100km/h, maybe several times a minute. It appears to fluctuate a lot more in hilly country but then it is much harder to maintain a constant speed. The head-up display also reveals that when you have cruise control engaged, the speed does vary by quite a bit; more than you might think and that is apart from the normal over-speed that you get with cruise control when on a long down-hill slope. Overall, the GPS head-up display is a worthwhile addition. I find that I only occasionally glance at the speedometer now, since the HUD is always there and it is much more accurate anyway. 16  Silicon Chip However, there are drawbacks to the GPS HUD. First, when you first start up in the morning (or whenever), the GPS can take quite a while to ‘acquire’ the satellites and give a valid speed reading. During that time it just flashes three dashes on the digits. If there is heavy cloud cover, it can take up to five minutes to give a speed reading. Second, GPS doesn’t work at all in tunnels or in city streets where there are lots of tall buildings, so again all you get is three flashing dashes on the display. In the overall assessment of the total human condition, this is not a big problem but there is another way and that is to use an OBD-derived head-up display. So having purchased the GPS HUD above, I had a look on the internet for a HUD based on OBDII signals. Lo and behold, they are available and generally cheaper than the GPS-derived units, to boot. I duly plunked for an iFOUND unit made by Founder Technology Group Co Ltd, in China and available on eBay for $75.69. This connects to the OBDII socket found in virtually all modern cars, typically positioned under the dash to the right of the steering wheel (ie, in right-hand drive cars; it’s the opposite in left-hand drive cars). You need to check whether your vehicle has an OBDII socket before you consider purchasing one of these head-up display units. OBDII stands for “on-board diagnostics, version two” and is a nowstandard vehicle interface designed primarily to allow mechanics to check and clear engine computer fault codes and monitor vehicle operation in realtime for fault-finding and tuning. The particular OBDII HUD I purchased decodes some of the data available on the OBD socket to display speed in km/h, fuel consumption in litres/100km and engine RPM. It also has the option of displaying coolant temperature or battery voltage instead of the vehicle’s speed at the touch of a button. However, the overall display is much more elaborate than the simple GPS-derived unit discussed above. Three large digits provide the speed readout (or battery voltage or coolant temperature) while three smaller digits above give the fuel consumption. siliconchip.com.au Engine RPM is displayed in a curved bargraph which changes from green to red at the top of the rev range. Plus there are a few other symbols for the alarm functions (speed, coolant and battery voltage), gear shift points etc. Again the display is inverted and transposed left to right, so that the windscreen reflection can be read. The iFOUND unit comes in two parts: the HUD itself and a metre-long flat cable with a plug which you fit into the car’s OBDII socket. The unit has a slide switch to turn it on or off and four buttons which you can use to change the display mode, set alarm levels and set gear shift points etc. Installation is similar to the GPS HUD reviewed above. The HUD unit is positioned forward of the instrument binnacle and arranged to reflect off the windscreen. A piece of semi-transparent plastic is provide for this purpose (as with the GPS HUD). The cable connection is much more convenient and neater than the GPS unit because it effectively runs up from under the dash (near the steering wheel) and can be run between the door and the side of the instrument panel. Again the OBD unit has an LDR to sense ambient light but in this case, while display brightness is adequate at night, it is anaemic in sunlight. As an aside, when driving at night I noticed that the display brightness was fluctuating and I finally twigged that the unit was dimming the display each time I passed underneath a bright street lamp. This is annoying, to say the least. I fixed it by disabling the LDR. I disassembled the unit and measured the LDR in bright light and darkness. It varied between about 12kΩ in darkness to less than 4kΩ in bright light. I soldered a 4.7kΩ resistor across the LDR and now the brightness is constant. Possibly, it is slightly brighter than ideal at night-time but it’s still too dim in bright sunlight. Using it At start-up, the OBDII-based unit initially displays ‘HUD’ and ‘101’ and then briefly flashes the whole display, including the RPM bargraph. As soon as the car moves, it gives the speed and the fuel consumption which is very high initially but then drops to more reasonable figures as you build up speed. I was able to compare speed readsiliconchip.com.au Driving with the iFOUND OBDII-based head-up display. The instantaneous fuel consumption readings give continuous feedback on your driving style and help you to save fuel. ings from the GPS and OBD HUD units and the differences were interesting. The OBD unit seemed to update at about the same rate as the GPS unit and was generally within 1km/h. So if the OBD unit came up to 60km/h (say), the GPS unit would show 60 and then maybe flick to 61km/h. In other words, the OBD display is more accurate than the vehicle’s speedometer but slightly pessimistic with respect to the GPS reading. At higher speeds, the units diverge more. At around 80-90km/h, the GPS reading was typically 2km/h higher than the OBD unit. At the time of writing, I had not driven on any of Sydney’s toll-ways or freeways so I cannot comment on whether the trend worsens at higher speeds. So while the OBDII HUD is more accurate than my vehicle’s speedo, I will always have to allow for the discrepancy between it and the GPS reading in setting the cruise control. However, I came to the conclusion that the OBDII unit is probably even more useful because of its fuel consumption readings (my 2004 Honda Accord lacks this facility), since it gives you continuous feedback about your driving style. If you step on the gas as you move away from the lights, the instantaneous fuel gulp can easily rise well above 45 litres/100km. Take it more easily and it might start at 12 litres/100km and then drop to less than 4 litres/100km as you gingerly caress the throttle to keep up with the traffic. Better still, if you coast as much as possible on a trailing throttle (ie, foot off the pedal), the reading will drop to zero provided the speed is above about 50km/h (in my Honda Accord). This indicates injector cut-off and it is surprising just how far you can travel in normal traffic while not consuming any fuel at all. Such information is vital if you are concerned about reducing fuel consumption. It confirms my habit of driving ‘far ahead’ to anticipate traffic hold-ups, red lights, lane blockages and so on. This and the continuous fuel reading can be very effective. It becomes a bit of a contest but I would never go so far as ‘hyper-milers’ who can obtain extreme results by coasting with the engine off for long distances, tail-gating trucks and buses and other driving behaviour which can be extremely hazardous. Incidentally, when the car is stationary and the motor is idling, the fuel consumption reading changes to litres/ hour and is typically 0.7 litres/hour when the engine has reached normal operating temperature. So I regard the OBDII HUD as more useful than the GPS unit, even though I would like the display to be brighter. But there is a third way, and Nicholas Vinen takes up the story on the following page . . . September 2013  17 Option 3: using a smart phone & an OBDII-To-Bluetooth Adaptor By NICHOLAS VINEN A typical OBDII-to-Bluetooth adaptor. They’re available via websites such as eBay and Ali Express for around $10. It plugs into the card’s OBD port and you can pair it with a tablet or smart phone. If your car lacks a digital speedo, you can make up for it with a smart phone, an OBDII-to-Bluetooth adaptor and some free software. You can choose from a range of display options and arrange them on the screen to suit your tastes. This third option involves using a smart phone. All you need is a lowcost OBDII-to-Bluetooth adaptor and a dashboard/windscreen mount for your phone – which you may already have anyway, if you use the GPS on your phone for navigation while driving. It also gives you access to data from the engine and body computer such as speed, RPM, engine load, coolant temperature and battery voltage which can be displayed on the phone’s screen. In fact, if your phone has built-in GPS, you can get the vehicle speed and GPS speed side-by-side. On our test vehicle, we found that they matched very closely when in a constant-speed cruise on level ground; typically within less than 1km/h of each other. Note that while GPS speed is shown with one decimal place, the OBD-II speed appears to be rounded to the nearest integer. Where to get the dongle The required dongle (OBDII-toThe OBD port is found under the dashboard, typically just to the right of the steering column (in a right-hand drive car). Power for the unit is derived directly from the OBD port. 18  Silicon Chip Bluetooth) is inexpensive and is available from multiple sources via websites such as eBay and Ali Express. For example, we bought ours from “Shenzhen win-win Electronics Technology Co Ltd” for the princely sum of US$8.50 with free postage via China Post; see http://www.aliexpress. com/item/Latest-Version-V2-1-SuperMini-ELM327-Bluetooth-OBD2-Scanner-ELM-327-Bluetooth-For-Multibrands/808159089.html Note that China Post can be slow; Hong Kong post is a faster and more reliable option, if available. Mounting it We used a goose-neck windscreen mount from Jaycar (Cat. HS9002) to place the phone right in the bottom corner of the windscreen. While this isn’t quite as good as a HUD, it’s certainly more convenient to glance at than a dash-mounted speedometer and you still have the benefit of a digital read-out which some people find much easier to interpret than a needle on a dial. One problem is that virtually all smart phones have shiny screens and if driving in bright sunlight, reflections of the driver’s shirt or objects behind the car can obscure the display. But despite this, the read-out generally remains legible under most lighting conditions and is especially good at night. As well as the phone and the Bluesiliconchip.com.au This view shows a Samsung Galaxy Tab2 tablet paired with an OBDII-toBluetooth adaptor and running the free Torque Lite app from the Google Play Store. You can display a variety gauges and graphs in various forms using information derived from the OBD port. tooth OBDII dongle, which plugs in under the dashboard (and is so small that you can hardly notice it’s there), you need software running on the phone to communicate with the car and interpret and display the data (an “app”). siliconchip.com.au We downloaded a free version of a program called “Torque Lite” (from Google Play) which works on most Android phones and tablets. iPhone/ iPad users will have to use different software such as DashCommand, although this isn’t free. Torque Lite works reasonably well although it has a few bugs and it drains the phone’s battery pretty quickly when in use. That’s partly due to the fact that the screen must stay on the whole time. There’s a non-free version too, which costs a few dollars and has more features. The battery on my phone (an HTC Velocity 4G) lasts about three hours with Torque Lite running so for anything but a very long commute, you just need to recharge the phone overnight. That means no cables – great! For longer trips though, it will be necessary to run a charging cable from the car’s accessory power or cigarette lighter socket to keep the power on for the duration of the drive. There are a few other little issues with using a smart-phone as a speedo. For a start, if you happen to get a phone call while driving, you lose the Torque Lite display on the screen (at least temporarily) and you have to revert back to using your car’s regular speedometer – even if you are using a hands-free system (and yes, hands-free Bluetooth still works while you are accessing the OBDII dongle). Also, if you have a screen lock enabled, this may activate after the phone call and you’ll have to wait until stopped to unlock the screen (we found this happened inconsistently, perhaps depending on the length of the call). That could perhaps be avoided by using a dedicated iPhone or Android device but that’s a much more expensive proposition. Also, we once had the phone spon- September 2013  19 Excerpt from ADR 5.2.6. the test instrumentation used for measuring the true vehicle speed shall be accurate to ± 0.5 per cent; 5.2.6.1. the surface of a test track when used shall be flat and dry, and provide sufficient adhesion; 5.2.6.2. if a roller dynamometer is used for the test, the diameter of the roller should be at least 0.4 m; 5.3.The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above [40km/h, 80km/h and 120km/h], there shall be the following relationship between the speed displayed (V1) and the true speed (V2). This screen lets you choose the display format for each readout, eg, dial, graph or digital display. You can customise and add displays to multiple pages. 0 ≤ (V1– V2) ≤ 0.1 V2 + 4 km/h This is where you use Torque Lite to select what you want to display. There’s an impressive list of data to choose from (much more than shown here). taneously reboot while we were using it which was a bit annoying. Plus you may need to clean the screen before clipping the phone into the dashmount holder as greasy fingerprints on the touch-screen (perhaps more accurately termed “smudge-screen”) can interfere with readability. By the way, the Bluetooth adaptor runs off power drawn directly from the OBDII socket and while we haven’t measured just how much current it draws, it should be somewhere in the range of about 5-50mA while operating. We left it plugged into the car over a long weekend and the battery still had plenty of charge to start so you can pretty much leave it plugged in all the time except if you will be leaving the car to sit for a week or more (or unless your battery is on the way out). Removing or re-installing it is a pretty quick and easy exercise but if you do that too often, you may wear SC out the connector. Issues Getting Dog-Eared? Are your SILICON CHIP copies getting damaged or dog-eared just lying around in a cupboard or on a shelf? REAL VALUE AT $14.95 PLUS P & P Keep your copies of SILICON CHIP safe, secure and always available with these handy binders Order now from www.siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number or mail the handy order form in this issue. *See website for overseas prices. 20  Silicon Chip siliconchip.com.au