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Forum Index : Microcontroller and PC projects : Reducing the current draw on a SSD1963
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| MMAndy Regular Member  Joined: 16/07/2015 Location: United StatesPosts: 91 |
Reducing the current draw on a SSD1963 TFT display board for battery operation. There are many conflicting numbers for the backlight current draw. I found one at 620 ma. and another at 330 ma. for the 7" TFT display board. Are there other ways, other than reducing the backlight from 100% to 50%, to reduce the overall current draw for battery operation? edit addition ... There are two ways to power the TFT backlight. One is applying 5V and the other is just using the 3.3V supply to power the TFT. Which is better to reduce the current draw? |
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| WhiteWizzard Guru  Joined: 05/04/2013 Location: United KingdomPosts: 2794 |
I have found that each (SSD) LCD Panel has to be considered in its own right. At the end of the day it is all about having an image that you are happy with. It is very much a balancing act between voltage, BACKLIGHT, series resistor and on top of all this, TFT quality. I have some TFTs that draw lower power at 5v, and others that draw lower at 3v3 (depends on vRegs they use I guess). Don't be afraid to play around with all these things remembering there is no one answer that fits all TFTs. WW For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9063 |
Bigger displays normally suck more current, as they have a bigger array of LED's for the backlight. Thus, NORMALLY, the bigger the physical display, the higher the backlight current consumption will be. That is not set in stone, and this is on theory. You could have a routine that turns the PWM for the backlight off, reducing the current consumption drastically after five seconds or so, and when the MM+ touch interrupt registers any touch at all, it brings the backlight back up again. That would probably be about the best way to deal with it, as these big screens on batteries is a big ask, unless you have very juicy batteries!  Smoke makes things work. When the smoke gets out, it stops! |
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| MMAndy Regular Member Joined: 16/07/2015 Location: United StatesPosts: 91 |
Keyboard 100 ma. + TFT 7" Display Backlight 620 ma. + TFT 7" Display electronics 100 ma. + Microcontroller aka MicroMite+ ~ 75-100 ma. = Total current draw about 1 amp. (worst case) 20,000 or even 30,000 mAh. 5V USB power packs can now be purchased at a reasonable cost. A 20 or 30 hour runtime could be possible. 
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| srnet Senior Member  Joined: 08/08/2014 Location: United KingdomPosts: 164 |
Whats a 'reasonable' cost ? $50SAT is Silent but probably still working. For information on LoRa visit http://www.loratracker.uk/ |
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| MMAndy Regular Member Joined: 16/07/2015 Location: United StatesPosts: 91 |
Just a ref. not an endorsement ... http://www.amazon.com/Poweradd-20000mAh-Portable-Technology-Blackberry/dp/B00MLVPOUM |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2794 |
PLEASE be careful of any of these 'bargain priced' power packs. There is a real safety issue with these types of 'cheap' products. Only last night I had to throw a similar item outside onto the grass as it started 'clicking loudly'. It was not under any load, it was just sitting on a table and everyone in the room started hearing a 'strange' noise. It took a few seconds to locate what was going on but the battery-pack went straight out of the door. By the way, it was not warm in any way, but it had left a 'burn' mark on the table. When I looked at it this morning I noticed it had leaked a chemical by a surprising amount; so it went into a sealed bag and straight down to the local garbage dump. Genuine power-packs with capacities like these cost considerably more than US$75; some are well over $200. There is no problem with anyone 'experimenting' with 'cheap' devices - but I feel it is important to make you aware of the 'risks' of an item like this that may at first appear to be a 'bargain'. For anyone wondering why I had one, it was a friend that had brought it round to have it to charge their tablet and he didn't want to leave it in the car outside (i.e. it wasn't mine!). WW For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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| MMAndy Regular Member Joined: 16/07/2015 Location: United StatesPosts: 91 |
With Amazon "Prime" they will take your "sealed bag" back for a full refund!
Besides, their user product reviews helps new buyers to weed out the inferior products from the quality products. |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2794 |
Trust me, if this had of been my item, then I would have wanted more than a refund! Literally a 'time-bomb' waiting to go off 
I totally agree; have you read the first review (the one with just one star). Like I say, nothing wrong with 'cheap' devices until they have a potential impact on your personal safety . . . For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
Well it has the word "BOOM" as part of the URL, so what do you expect. :) Microblocks. Build with logic. |
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