On Tue, Dec 9, 2014 at 4:05 PM, joem joem@martindale-electric.co.uk wrote:
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.
there's a guy who has managed exactly that [reverse-engineering]... let me find his paaage.... ah here we go: http://tech.mattmillman.com/lcd/rm5251/
he created a tool that modifies the binary so that you can select whatever you want.
if you have one of those boards can i ask you the favour of locating the white LED circuit and sending me a macro-zoom photo (both sides) of that section of the board, highest resolution you can?
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.
pin 30 of the HSD101PWW datasheet is "LED PWM brightness".
The example circuit is given in their PDF.
i found the application note: http://www.elecinfo.com/upload/community/2013/12/30/1388365231-20314.pdf
the circuit is *radically* different from the [proven, working] one that has been in circulation for years. it involves an RC circuit with a link into the FB: EN/PWM is used purely for "EN" and the FB line is given an extra "kick" periodically via a PWM to fool it into switching off.
all that has to go, which leaves me in a position to need to understand how the circuit (that i copied) works, and adapt it.
... or find an alternative.
(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.
unfortunately i don't have the luxury of being able to experiment like that. remember that i am endeavouring to *establish* this business, i am not operating from the position of having an R&D budget from established business funds and established sales in order to make these kinds of experiments.
so my preferred path is to use a pre-existing proven circuit. this is proving hard to track down.
last resort i will make something [conservative] and test it. my primary goal here is to get a working prototype that can begin a 2nd crowdfunding campaign.
Obviously not clever if it has to work from batteries
yes, this does.
- 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.)
ack. thx joe.