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cubeberg

LCD Suggestions?

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Ribbon cable with one end having loose single female ends and the other having 1 solid female end.

That will probably be the best solution.

 

In the mean time, I did a little experiment with charge pumps. I got -25V by cascading three 7660's. This is pretty much what they do for some small LCDs, but I've never seen more than two of them cascaded. The display worked, but still needs some tweaking.

 

Meant to comment on this, but haven't had time to look up that part until now. Looks fantastic!

 

Any idea how much current is needed? I'll have to test my LCD. That seems like a much simpler solution (and cheaper? much lower part count) than the other chip you suggested.

National's datasheet provides a schematic for getting -15 out of 5v with 2 devices. I've used the 5v usb power off of the LP in several projects.

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I am trying to multiply 3.6V three times (3.6 * 2 * 2 * 2 - 3.6 = 25.2V,) but this is not working quite well.

 

The problem with 5V is that you get just under -15V. When I test it without back light, it works, with back light, voltage drops below what LCD needs. I did try MAX660 (100mA,) TC7660 (20mA,) and TC7662B (20mA.) MAX660 and TC7662B worked the best.

 

MC34063 is a lot cheaper, more stable, and more versatile than those charge pumps, but requires more parts, coil in particular. I think I will stick with MC34063.

 

Speaking of power supplies, I am working on a board with 5-6 different power supplies on it. Any ideas? I want to have one charge pump, two step-up, two step-down, and maybe one more, dual voltage.

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When I test it without back light, it works, with back light, voltage drops below what LCD needs.

I'm not planning on using the backlight for the other LCD - 420 mA at 4.2v is a decent current. Is the source battery's voltage dropping under the load?

 

MC34063 is a lot cheaper, more stable, and more versatile than those charge pumps, but requires more parts, coil in particular. I think I will stick with MC34063.

Makes sense - it's supposed to deliver a fixed voltage, even under changing input voltage - correct?

 

Speaking of power supplies, I am working on a board with 5-6 different power supplies on it. Any ideas? I want to have one charge pump, two step-up, two step-down, and maybe one more, dual voltage.

 

Is it a Power BoosterPack? What's the target use? It'd be nice to allow power via something like a LiPo, but provide 3.6 or 3.3 (LP) and 5v (peripherals requiring higher voltage - LCD, etc). Charging would be helpful in that case as well. Maybe even 1.8v?

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When I test it without back light, it works, with back light, voltage drops below what LCD needs.

I'm not planning on using the backlight for the other LCD - 420 mA at 4.2v is a decent current. Is the source battery's voltage dropping under the load?

USB voltage is dropping a bit.

MC34063 is a lot cheaper, more stable, and more versatile than those charge pumps, but requires more parts, coil in particular. I think I will stick with MC34063.

Makes sense - it's supposed to deliver a fixed voltage, even under changing input voltage - correct?

Correct.

Speaking of power supplies, I am working on a board with 5-6 different power supplies on it. Any ideas? I want to have one charge pump, two step-up, two step-down, and maybe one more, dual voltage.

Is it a Power BoosterPack? What's the target use? It'd be nice to allow power via something like a LiPo, but provide 3.6 or 3.3 (LP) and 5v (peripherals requiring higher voltage - LCD, etc). Charging would be helpful in that case as well. Maybe even 1.8v?

I was thinking about something small and universal, something you can use for any project. Come up with 5 or 6 different solutions, for example one MC34063 based step-up, one step-down, etc. Something similar to what I did here, just all power supplies.

Charger sounds good, will look into it.

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Like this? (PDF - check out page 9)

It's a step up/down/inverting evaluation board for the 34063. Of course it's $70 at digikey.

 

Are you looking for a DIY type module, or something that would provide certain power with a bunch of different power sources (9v, AA pack, LiPo, etc).

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OK, inverter is working as it should, though I am one LaunchPad down. TUSB & 2553 didn't take accidental 18V too well.

LCD's memory controller got damaged too, this might be the end of my T6963 adventures :)

 

Those values are just for testing (efficiency is horrible, the coil has to be a lot bigger for the small amount of current LCD is drawing.)

Ct = 330pF, Rsc = 2ohm, L = 220uH, Co = 100uF, R1 = 5.6k, R2 = 82k

post-197-13513553951_thumb.gif

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OK, inverter is working as it should, though I am one LaunchPad down. TUSB & 2553 didn't take accidental 18V too well.

LCD's memory controller got damaged too, this might be the end of my T6963 adventures :)

 

Those values are just for testing (efficiency is horrible, the coil has to be a lot bigger for the small amount of current LCD is drawing.)

Ct = 330pF, Rsc = 2ohm, L = 220uH, Co = 100uF, R1 = 5.6k, R2 = 82k

[attachment=0]inverter.gif[/attachment]

 

Ouch - that sucks. At least it wasn't a $30 lcd, but still.

 

I still haven't measured the current draw, but I'm getting ready to start working on the second LCD I bought for another project. Did you do the optional filter, or is that mostly used for higher-current?

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Idd current is 8mA and from what I can see, Io current is around 1mA.

The inverter I was using had no filter (though I could use one, my laptop's power supply is just horrible.)

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Going back to GLCD board.

2" x 2", 20 pin single row plus 10 pin dual row connector, 20 pin dual row header to map the pins (wires could be used,) 5V power, 3.6V LDO to power LP or MCU, -18V LCD switcher, dual supply transceiver, optional MCU which would act as a serial-parallel bridge.

 

post-197-135135541597_thumb.pngpost-197-135135541603_thumb.png

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I found another interesting one on ebay it's a 3.2" with touch and an sd card slot. System will not let me provide a link yet. A great value too at 16.95 US.

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Is this a backpack layout?

No, the idea is to have something that you can just plug to any GLCD and not worry about level shifting or negative voltage.

 

I found another interesting one on ebay it's a 3.2" with touch and an sd card slot. System will not let me provide a link yet. A great value too at 16.95 US.

Are you talking about those:

3.2" TFT LCD Module Display + Touch Panel + PCB adapter

3.2inch 320x240 Touch LCD(A)Screen Touch SPI ADS7843,LCD SSD1289 TFT LED 320*240

Very tempting :)

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