Gamma control by light sensor

**kronos** · 02-22-2005, 10:31 PM

Originally Posted by stevieg

boostedGT-S, using a relay connected through your lights you could make a similar circuit that therefore runs off your car's sensor though it would probably need the line high setting reversed to work? (sure someone could correct me on this)

I updated the program to accept another parameter so you can set it to reverse depending on your sensor (i.e. if it outputs a signal if lighted or if not lighted), although this could be easily accomplished with a SPDT relay by connecting the 'normal open' pair of contacts so when the lights turn on it also brings CTS high.

mgithens what about using a couple of photocells: a separate one and the other in a delayed circuit (around 1 sec or maybe less) and by comparing the states when the delay circuit triggers you can tell if it's really night or it was just a shadow from a light pole or something (both must be illuminated or not to detect the event); that way you can shorten the reaction time and still have a good amount of error filtering. I'm thinking if you enter a short tunnel by the time the 10 secs pass and the dim turns on you are out of the tunnel.

**mgithens** · 02-23-2005, 12:38 AM

well I switched my 3300pF cap for a 100pF and it makes the swing you are looking for... photocells are MOST sensitive to direct light, but ambient light is still very much a factor... so by changing the capacitance you can adjust the reaction time... think of the capacitor as a small bucket, the electricity pours in and the circuit stays level (for the most part) and if the shadow goes away quickly then the light change would go unnoticed... but if it persists then the light on the screen will dim to match the surroundings...

if the tunnels are really that dark, then you should consider using darker color backgrounds, for instance a white lettering on a med dark blue background won't blind you when you hit the tunnel... but I dont' think a circuit needs to respond faster than your eye will, and I think that is the direction that it sounds like you are heading... I will post a circuit tomorrow after work... it really does work well and I will post full videos after my completion (not any time soon)...

I am also working on a temperature circuit... at first I was thinking that I would just keep the CPU from booting when temps dipped below freezing, but now I am set on the idea of a really small heater/light bulb to keep the hard drive above freezing... I am thinking a 10watt bulb will do the trick... and I found a mechanical thermostat that would help reduce electrical consumption... Rittal SK 3110... pretty slick device... but I will save that for another thread... hopefully it will be installed this weekend... in the summer I will switch it over for a fan type unit to kick on when CPU bay temps (when booted) get over the 120degF threshold...

**DeltaFX** · 02-23-2005, 05:04 AM

And you can use this sensor with a tiny piece of software that computes twilight/sunrise/noon/sunset/twilight/ where you are, using lat/lon coordinates.

**stevieg** · 02-23-2005, 07:03 AM

Originally Posted by kronos

I updated the program to accept another parameter so you can set it to reverse depending on your sensor (i.e. if it outputs a signal if lighted or if not lighted), although this could be easily accomplished with a SPDT relay by connecting the 'normal open' pair of contacts so when the lights turn on it also brings CTS high.

mgithens what about using a couple of photocells: a separate one and the other in a delayed circuit (around 1 sec or maybe less) and by comparing the states when the delay circuit triggers you can tell if it's really night or it was just a shadow from a light pole or something (both must be illuminated or not to detect the event); that way you can shorten the reaction time and still have a good amount of error filtering. I'm thinking if you enter a short tunnel by the time the 10 secs pass and the dim turns on you are out of the tunnel.

My thoughts are about your software is that is could be very useful for a WIDE range of uses without having to go out and buy a proper relay/interface board... if it could run a program (gamma on/off) in the ini It could then be adapted to other uses, such as a reverse camera, or disabling play of video/dvd whent he handbrake is off.

For the screen gamma, I think I would rather fit a relay across the lights so when I turn them on, it does the screen gamma... And then if I want auto-gamma/lights I would fit the mod to the lights instead!

**kronos** · 02-23-2005, 09:05 AM

Originally Posted by stevieg

My thoughts are about your software is that is could be very useful for a WIDE range of uses without having to go out and buy a proper relay/interface board... if it could run a program (gamma on/off) in the ini It could then be adapted to other uses, such as a reverse camera, or disabling play of video/dvd whent he handbrake is off.

For the screen gamma, I think I would rather fit a relay across the lights so when I turn them on, it does the screen gamma... And then if I want auto-gamma/lights I would fit the mod to the lights instead!

I made a modified version to run a program in the ini instead of setting the gamma (and if you want I'll give you the source code which is very simple so that you can modify it to suit your needs if you please). About connecting the mod to turn on the lights I don't know... I always turn them on, even during the day, so that I can be better seen on the road by the others, in which case it would mean that my screen would be dim all the time.

**Blue ZX3** · 02-25-2005, 02:26 AM

I don't think that I even thought about just controlling the screen itself...thats a cool idea... but like mentioned above, some people don't want to mess with their screens after shelling out the funds.

**mgithens** · 02-25-2005, 06:26 PM

well, I think a simple picture walk through of what is involved will clear that issue up... building a ready made circuit is not really an option, but the circuit is SUPER easy... like 5 parts... I will get it done soon enough and put some videos up...

**TimmyM** · 02-25-2005, 06:30 PM

I think I would be interested in controlling the screen also. I don't want to use another serial port if i don't have too.

**stevieg** · 02-28-2005, 09:58 AM

Been out, bought some bits. I forgot the diode though.

I got a phototransister AND a photodiode.

Would a photodiode do the job of the phototransister+diode?