LCD 7 segment vs. LED 7 segment display?

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FastEddie

Joined Jul 14, 2007
35
Hi. I'm trying to make a small project that requires two 7 segment displays. I'm using a PIC 16F818 to run it. Due to the limited pins I multiplex(?) two 7 seg LEDs together using npn transistors. This seems to work pretty good, but I was wondering if I use LCDs instead...

Can I multiplex LCDs as I could with LEDs?

Battery life should be longer?

Do I need a resistor in series with each segment, if so, any idea how much?

I realized that the LCDs that I ordered (Mouser part# 696-LCD-S301C31TF), if I read the data sheet right operates on 5VAC and I'm using 5VDC. Will this work?

Any thoughts are welcomed. Thanks in advance.
Ed
 

SgtWookie

Joined Jul 17, 2007
22,230
Can I multiplex LCDs as I could with LEDs?
Similarly.

Battery life should be longer?
Quite probably.

Do I need a resistor in series with each segment, if so, any idea how much?
The specifications don't indicate current utilization, and the link to their catalog on their website is not currently functioning. You should call them.

I realized that the LCDs that I ordered (Mouser part# 696-LCD-S301C31TF), if I read the data sheet right operates on 5VAC and I'm using 5VDC. Will this work?
According to the docs I've read, you must use AC. The absolute maximum limit specified for DC levels is 3V.

See here:
http://www.lumex.com/viewer.aspx?file=technotes/LCD_dispwodriv.html#Characteristics

Their telephone #: 800-278-5666
 

SgtWookie

Joined Jul 17, 2007
22,230
Ahh, that's not exactly what I meant ;)

Why don't you give them a call, and verify what the requirements are for driving their LCDs?

I DID see a couple schematics for power supplies for their products, but it's rather confusing because the power supply schematics were purely DC, whereas the "datasheet" specifies 5VAC for the exitation voltage, and in another location on their website it specifies absolute maximum to be 3VDC.

Perhaps the exitation they require is simply 5v p/p with an average around 1v. I don't know. That's why I suggested you give them a call. It's a toll-free number.
 

Nomad

Joined Oct 21, 2007
43
batteries would definately last longer. if that pic supports it you can use it's hpwm to generate an ac source if needed. some 5v pics have a wide operating voltage range. the 16f628 will operate from as low as 2v up to 5.5v. i dont have access to the data sheet for yours to check. EDIT: just checked. yours does have hpwm and the wide operating voltage range!
 
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