Hi Tom.
This is amazing.
Just curious how these could be mounted or held together in a case? Are there holes for standoffs?
Also how much power would be required to drive one board?
Mark
LED Donation to VHS - SMDs mostly 3014 - help yourself
TomKeddie
#19
At the moment I’m torn between simplicity (just use resistors) and complexity (use a constant current source). I’m learning toward complexity since it also gives dimming control which would make a more interesting sign but it adds about $5 per digit so perhaps not. I’ll probably do both eventually.
More than 0, no limit on number.
Not yet but there will be. I’m trying to decide whether to bring the power in using the standoffs, this seems to be simplest but might be a bit limiting. It does get around the problem that all the current needs to flow along the back otherwise (things get tricky once you pass 1A or so).
This really depends on the leds. For a sign you don’t want full brightness because it will hurt to look at it. The number 8 is about the most complex with 10 out of 16 segments lit, assuming the leds work at 10mA, an 8 would be 100mA. So lets say about 100mA per digit but less might work? This is at 12V so 1.2W per digit.
Hekseskudd
#20
yeah these LEDs are 65mA each, and it even says they are harmful to look directly at on the dat sheet.
TomKeddie
#22
I’ve sent v1.0 to oshpark, will take a few weeks. I ended up with a constant current source on the back, cost could be as low as $2 and it lets you do pwm of each digit.
Clearance on the mounting holes is too tight, will likely need to shrink them to 2.5mm in next rev.
I’ve put pads on the back for both side to side connection and SMD pin header mounting.
The constant current source is the same schematic as the femtobuck.
One quirk is that there are up to six leds required on the back. These are needed to bring the short segments up to 3 leds and thus balance the current evenly across all segments. People can likely cover them with some black goop if needed.
TomKeddie
#25
So I grabbed some leds at the MMC event last night and put one onto a power supply just now. As you might expect they are really bright. Even at 10mA it feels like you are looking at an arc welder. At 5mA they’re bearable so I’ll design my sign for 5mA.
I suspect that better results will be seen using pwm on the CC supply or using a diffuser.
PCBs have not arrived yet but they should be here any day.
My next PCB will be for a working lamp I think. Will probably use the whole 10x10 pcb with a mount hole in the centre.
TomKeddie
#28
Could be but these are all warm white, personally I prefer something cold as a work light. There’s also the thermal thing, kinda needs to be an Aluminium PCB.
TomKeddie
#30
What voltage are you driving them with?
Something running at 110V like this would be neat.
or this one would be more likely circuit but in the floodlight form factor. This one is scary because he boosts the mains!
TomKeddie
#33
I’ve published the files at https://github.com/vhs/vhs-pcbs/tree/master/led-segment-display
This still a work in progress
- need to test power supply
- need to add an indicator to show the top of the display
TomKeddie
#36
I’ve finished testing my project and it works well. Final code and pcb designs are at https://github.com/TomKeddie/prj-led-segment-display
If there is enough interest we can share a dirtypcbs panel with lots of these boards.
chadleaman
#38
Could you conceive these being used to make an electronic name badge – like, have someone’s name on it as a wearable? I / my team spend a bunch of time on tradefloors and conferences so “name in lights” could be a good conversation starter.