Hi,
I'm a long time forum reader, but first time poster, so please be nice.
I built a tiny device with a 128x64 I2C OLED display and an ATTINY85V-10PU, powered with 3AAA battery. I would like to minify the project, so i want to change the 3AAA battery to a CR2032 coin, but the OLED display consume too much power for long time running. That is why i would like to change the display to a Nokia 5110 LCD without backlight.
I ordered a display from here: https://techfun.sk/en/product/nokia-5110-lcd-display/
I made a simple test program on the Attiny, to test all bias and contrast combination.
It's working perfectly with:
Arduino 5V power source (I use Arduino Uno as ISP)
Arduino 3.3V power source
3AAA battery
2AA battery
But when i try it with a 3V cr2032 coil, nothing showing up on screen. (Tried with every bias/contrast combination)
The specification says it's minimum operating voltage is 2.7V, the cr2032 has 3.01V (measured with multimeter) but not working.
I don't have a wiring diagram, but the device contains only the Attiny and the display, no other devices. The power supply is the same for the controller and the display, and the only other wiring is the SPI connection between the controller and the display.
Is 3V not enough for the LCD? But then why 2AA battery is enough?
Is there any easy and power (and size) efficient way to step up the voltage with 0.5V or 1V?
Is there charge pump IC-s, not boards, simple DIP IC-s?
Any idea, what is the problem?
Sorry for the long post, and thanks for the answers!
Did you check that while it was driving the 5110? If not, the reading doesn't mean much. If yes, I guess the connection is suss, and you might try pressing gently on the screen.
Without the backlight, the 5110 runs on practically nothing, so I imagine a 2032 would be OK.
Thanks,
I measured without load.
I think, i have huge gaps in my basic knowledge.
Can you give me an explanation, or a link about why the voltage is lowering in this simple circuit, please?
I measured on the display and it's only 2.8 volt. I found an another battery and with that the voltage on the display was 2.92V but still not working.
So it seems the display needs 3 or more volts to operate.
I found an old 3.3v step-up board and wired it before the display and is started working (with 3.28V), but now i have to find a solution to turn off the step-up board when the device is in sleep (because it's not too efficient), but all the pins on the attiny are already in use. But this is an another problem.
There is a thing with all power sources including batteries and that is there internal resistance. The internal resistance and connection resistance add to together to form a resistor in series with your load, that resistor will have a voltage drop following Ohm's law. Also as the battery depletes its internal resistance increases. The behavior you describe is what I would expect.
On reflection, I think I was probably wrong about the 2032 being OK. I was thinking about the 5110 only, and not taking your other gear into account. I don't know anything about your Attiny. Still, be aware that the 5110 can be a bit fragile!
I made some tests, and the conclusion is:
It can work with cr2032 if i step up the voltage to 3.3V, but the contrast is still very poor with the best bias-contrast combination.
The Attiny can work with very low power, from 1.8V to 5.5V and it consumes 3mA with the cr2032. And whole device is in sleep mode most of the day. (Approximately it's only awake 1 or 2 minutes a day) So ideally it can work for months with a cr2032.
But going back to the original problem:
I read in other threads that, the Nokia 5110 LCD operating voltage is 3V, and 5V can damage the display but, with 3.3V (from Arduino power source) the LCD is only barely working. Contrast is very poor even with the best settings. But if i supply with 5V it has beautiful contrasts with a lot of contrast settings.
Then what is the perfect operating voltage for the Nokia 5110 LCD?
Thanks,
I tried with two LCDs, and it worked somewhat. While i constantly pushed the metal part of the LCD the picture was good, but when i released the picture disappeared again. Both could only work while i pushed. Maybe i ordered it from a bad quality stock.
After that, i broke one of it.
I think, i will stay with the OLED display. This Nokia LCDs has too much problem with. Poor assembly quality, hard to find the good contrast value, it needs step-up board for the cr2032, it can break easily . And most importantly, with the step-up board it consumes too much power.
The 5110 packaged for Arduino are all factory seconds from Philips. I have had four of them for years on Megas and they all work fine, but one needs pursuading from time to time. Maybe I was lucky.
Try the LIR3032 battery. It is a lithium rechargeable Button cell that is 4.1 volts fully charged and will operate down to 3.1 volts before needs to be charged. You'll need to do some research on how to properly charge them without damage but they are quite useful.
