I'm looking for a small fast refresh, sunlight-readable, backlit display for a project.
It will display, in two rows/lines, a number of rectangles or vertical lines which represent a value, like this:
So, pretty straightforward, there are oodles of 16x2 LCD displays out there. Easy to find sunlight-readable and backlit displays like this. Ideally it would be more like 20x2 or even 30x2 (for finer increments), but 16x2 is fine.
The tricky part is the refresh rate. It's hard to find this in the spec sheets, but I think it's the Response time under Optical Characteristics.
Sometimes the optical characteristics aren't even stated. And I'm not sure what Response time (rise) vs Response time (fall) actually means but if that is the refresh rate, then the displays I've found thus far are way too slow - usually in the low hundreds of milliseconds. I need something more like 20ms.
Can anyone point me in the right direction? Thanks!
What is wrong with an LED bar module? By the way, OLED displays are very fast.
But, what is the reason for the refresh requirement? Human eye response time is not very fast.
The project is a visualiser of sorts for a metal detector's audio output, to allow those who are deaf or hard of hearing to use a metal detector.
To be mounted as needed, the display must be pretty small - maybe 3 inches wide, max. I couldn't find any LED arrays which could fit 16 or more LEDs in such a small place. A custom PCB provisioned for small SMD LEDs is an option but I'm exploring a display first. Maybe a module does exist though!
For the device to be functional, it needs to update many times per second and be low latency. Metal detector target responses are subtle with many variations over short periods of time.
Any noticeable latency will render it useless for pinpointing targets, which can be very small (tiny flakes of gold under 0.1g in mass, think sesame seed size). I think it will need a pretty fast display.
Finally, it needs to run off a relatively small, lightweight battery for 8+ hours. I don't think OLED displays can accomodate that requirement, but I'm happy to be proven wrong.
Thanks for your response and prompting more detailed requirements.
Instead of waiting to be proven wrong, why not go and read some OLED specification sheets? You know you can and should look this stuff up, right?
Latency is not the same as speed (bandwidth) - it really means "delay". Have you done any bench experiments to find out how some basic easy to source displays work with your existing (I hope) detection hardware?
What is the exact bandwidth of your detection hardware? What is your detection hardware?
That would be 3 x 25.4 / 16 = approximately 4.8 mm spacing. It doesn't sound hard to find.
A simple collection of 10 segment LED bargraphs would work. 4 of them organised 2 x 2 would give you 2 rows of 20 LEDs.
A quick look on Farnell UK and I found a Kingbright DC-10SYKWA (Farnell No 2079883). The datasheet shows a display 25.4mm (1in) long x 10.16mm (0.4in) wide. Two of them lengthways would be 2in wide. Two rows of the would be 0.8in.
Of course I know I can look this up. I searched for "sunlight readable backlit display" and found a ton of LCD and TFT displays that, as far as I can understand, are too slow. I even posted that I've looked at spec sheets and did my best to understand them.
I didn't know simple OLED displays for small projects existed, I'm only familiar with the types of screens that are in smartphones, which clearly aren't the right thing for this project. Thanks for the suggestion, maybe an OLED will work if I can find one that can be read in direct sunlight.
I understand latency vs speed. Much of the latency will come from the processing of audio, but still, if a display has a 50ms refresh rate, it is not suitable as it both results in excessive latency (from detector response to visual) and won't be able to provide close to realtime feedback to the user.
No, I haven't done any bench testing. I'm just starting this project and researching my options. Hence the post on the Project Guidance forum.
By detection hardware do you mean my metal detectors? I'm not sure how that's relevant, but yes, I have two detectors.
That's very helpful! Thank you for the reference, I didn't know these types of modules existed.
You're making a lot of guesses and unsubstantiated claims, upon which it seems you will screen all advice. So I'm out. Good luck.
There's dozens of them. Been around for decades! You can get some with more than 10 segments but you pay more and it's probably cheaper to buy 2x10 segment rather than a 20 segment.
You can also get ones with fewer LEDs and stack them with different LED colours if you want.