Citroen XM Forum

Was just wondering whether anyone knew what it would take to project vehicle speed onto the windscreen as a HUD like on the C6? Is it sophisticated or could something be stuck onto the screen to display?

I checked how good the XM speedo was today by comparing with mph on my iPhone - pretty close at 70, underestimate at 90 - and it crossed my mind that the problem is probably not getting the mph value but getting it projected onto the screen.

Cheers

Marc

I tried this, and messed about with "negative" LCD displays, and some LED ones, using upright digits that might read decently "mirror image". Failed to get sufficient brightness for daytime use, plus some annoying unwanted reflections at night.

My motivation for doing this was difficulty in reading the tiny km/h figures on our RHD/mph speedo quickly and safely.

Now have installed a small dash-top 3-digit green LED display, with 16mm digits, that reads out speed, switchable to either km/h or mph, and trimmable for accuracy. Unit is driven from an additional ABS sensor on a front wheel, using the existing ABS ring. Output goes to a F-to-V converter (tacho circuit), with the display being an LED digital voltmeter. Brightness of display is adjustable, and dims automatically when lights are switched on. Works a treat, and allows me to keep eyes on the road.

There are many aftermarket ones of different qualities but the easiest way to try it for yourself is to use a smartphone app, there are quite a few of those available in your favourite app store. It can get the speed from the GPS so no connection to the car is needed. The phone simply shows a mirror image of the display and you can see the reflection in the screen. Whether you find it good enough or not remains a question but it's easy enough to try...

Try dashboard for the iPhone. Works for me.

I've been wanting to do this for years.

There was a guy on the XM-L mailing list, think it was one of the Daves, who had an aftermarket unit in his V6 quite a few years ago.
It worked and looked very well, and fit really nicely onto the tilted bezel of the instrument cluster in the Series 1 cars.

Just trying to find the link, which of course I can't.

As Gábor says, the phone apps work somewhat well too.

Ciarán

S2s kinda lack that handy tilted bezel... I'll post some photos of the one I made.

I did have the thought that, rather than a dash-top unit (next best thing to a HUD), it might be neat to build a 3-digit LED display into the RH main dial - where the gear indicator is on an auto', but that takes the edge off a screen-area display.

A good head-up display needs a VERY bright display to work in daylight, especially if the road surface tends to be lighter rather than darker, or there's something light (white van, the sun...) in front of the vehicle. Most of the adverts for after-market units, or phone-apps for that matter, seem to feature either night-time/dusk conditions, or are photo-shopped efforts. Not only does the display need to have really bright digits, but the background (and frame of the unit) needs to be black. LCD units such as this http://www.conrad-electronic.co.uk/ce/e ... egory&rb=1 might be adapted with a brighter light source, and any pos-reading LCD display can be flipped to neg simply by inserting one additional polarising filter.

Had a good bit of fun trying to find a suitable display (neg, flippable R-L, potentially bright), but in the end I just went for one of these:
http://www.amazon.co.uk/s/ref=nb_sb_nos ... ltmeter%20
slightly modified.

That's really innovative what you've done Chris, with the extra ABS sensor, interpretation circuitry and display, impressed!

Ciarán

I never really missed a HUD but I tried it today, just for the fun of it. I tried this one: https://play.google.com/store/apps/deta ... uts.carhud

Rather simplistic but it works all right. Not visible in bright sunlight of course but it works from cloudy conditions to dark. Some aftermarket units I saw advertised come with a reflective screen layer adhering to the inside of the windscreen, that would probably help. If I wanted to use it permanently, I would probably look for a cheap and simple Chinese smartphone, not the latest and greatest, with just enough power to handle this app. (Well, this might be problematic for the poor souls out there with apple-like phones but let that be their problem [emoji2]). The phone case should be as black as possible and any remaining bright parts (like brand logos and similar) might still need to be covered with black tape or whatever. With the wonderful suspension of the XM it mostly stays where placed but a little patch of Velcro tape might help even that.

There are many more apps that can do more, turn to red when the speed limit is exceeded and similar. There are more ambitious projects on the web that use one of the current miniature computers like Arduino or Raspberry Pi but the smartphone approach can't be beaten for simplicity.

Chris, not wanting to spoil the fun of it but wouldn't it be easier to swap the speedo for a metric one?

Yes, I did think about that...maybe just changing the speedo fascia...and then built the digital one, which was much more fun.
Did play with digiHUD along the way, but no good in daylight, and a bit approximate.