On Tue, 2014-12-09 at 14:33 +0000, Luke Kenneth Casson Leighton wrote:
On Tue, Dec 9, 2014 at 8:49 AM, joem joem@martindale-electric.co.uk wrote:
On Mon, 2014-12-08 at 15:45 +0000, Luke Kenneth Casson Leighton wrote:
... *deep breath*... but.... hold everything, i've never been a great fan of the 1024x600 LCD panels
hmmm... thinks odroid-vu http://www.hardkernel.com/main/products/prdt_info.php?g_code=G140383714860
Miniature HDMI monitor for $120. I bought one. If there were more of these things around with variety then lessens need for fixed screen.
which reminds me: i need to work out a circuit for driving the LCD backlight. does anyone have e.g. one of these: http://www.adafruit.com/products/1931
I have similar but 5" from Aliexpress (used in reversing cars). When I try to replicate the board, came across this idea that there is some 'firmware' like parameters that have to be set up to make the chip and LCD work correctly. There was no further information about how one might go about doing that.
i need an example circuit to work from: the one that i have uses the SY7201 and it is designed to pulse the LEDs, whereas the Hannstar LCDs have their own dedicated LED backlight PWM input.
Not sure what that means. The example circuit is given in their PDF. (The inductor is worked out by swapping out some reasonable values until its just right which you can get by looking at the scope signals, or do some calculations to estimate best value.) The inductance changes with changes to LED chain. The LED chain is electrically isolated from the rest of the display - so nothing to worry about except burnt out LEDs. Net current down LED chain normally not exceed 20mA. That is how the limiting resistor is set.
(I normally use a 30V supply and limit the current to 20mA by having a serial resistor and upping the voltage until good brightness is reached. Obviously not clever if it has to work from batteries - but it is a starting point to work out the net LED voltage that has to be subtracted from calculations to get limiting resistor, currents, and inductance.)