I've bought an LCD module, but apparently it's not plug-and-play and needs some extra circuitry. So far I worked only with stuff that uses just power and logic I/O.

(module datasheet here, controller here)

There is no mention of what kind those capacitors should be... do they have to be ceramic or I can use electrolytic? Is the capacity important?

Hi Igor,

John has given a really great explanation here.

As rule of thumb when purchasing these, look for a ceramic 1nf capacitor that is cheap and sounds generic/boring - the ones it looks like they sell loads of.

In lots of cases you'll see capacitors like this in circuit diagrams, and they tend to be ceramic decoupling or bypass capactiors. The giveaway is usually:

• They are unpolarised
• They are generally marked as 0.1nf - 1.0nf, or not evan at all
• There are a handful of them, sometimes all in parallel just between Vcc and Gnd (the idea is you spread them out around the ic/pcb when laying out)

If they are polarised (one of the blocks isn't filled, and probably a + symbol), then they'll likey be >10uF electrolytic, more for protecting from low frequency/large power drop out.

Capacitors can seem like a bit of a minefield as there are so many of them; go to farnell ceramic capacitors section and you'll get 17k options :) But for example, Sparkfun don't even have a capacitors section, just a general components section. Here you can see there is a couple of ceramic (0.1nf, 22pf), and a few of electrolytic (10/100/1000uF). This gives a good indication of what you generally can get away with.

Most capacitors are used for decoupling or some sort of timing/RC circuit. With the first, you can be pretty much just choose the right type of capacitor, and be in the right ball pack for value (while prototyping!). Yours looks like a third case.

Simon

Thanks for the comments, guys.

I've looked into the controller datasheet and it's somewhat more helpful.

So it seems the capacitance is important after all... and they're used for the voltage booster(?), not decoupling. I guess for now I'll get a bunch of 1uF capacitors of both kinds and see how it works.

One thing I would add is about derating capacitors. A general rule is to derate by 50%. So if you have a capacitor between VDD and GND. (3V and 0V respectively) You want to get capacitors rated at 6 or more volts.

Alot of detailed explanations, but to answer the question; I would reach for 1uF Tants rated at 10V.

Hi Igor,

Did you get this display to run on USB-only current?  I'm thinking of buying one so anything you could share with me would be of interest.

Anders

Not yet. I assembled the circuit but can't make the display to turn on so far.

Well, after ripping out all wires and redoing the circuit from scratch I was able to make it work. Will try to up some code and pics later.

Picture here, will do a write-up and post code later.

Thanks for the help, everyone!