Hmm. Interesting. Is that etching with iron chloride? I don't have the software neither, and I like the look of neat wiring too!

 

Is that etching with iron chloride? I don't have the software neither, and I like the look of neat wiring too!

I use ferric chloride for etching. I use the freeware version of Eagle for schematic capture and PCB layout.

 

Aah! This is looking to be quite some fun! Let's hope we don't go back until September and the dog doesn't accidentally drink the FeCl3. I'll look at that software you recommend.
Thanks again

 

I use ferric chloride for etching.

? any additives (HNO₃) - ? temperature ? masking agent (? photoactive PCB)

 

I'll look at that software you recommend.

I use an old version of Eagle (4.13r1). The newer versions were requiring an account, but I don't like the look and feel of the newer versions anyway.

 

Hello there again Dennis,

Could I be a bit more cheeky and ask for a bit more advice? I've ordered the mosfets and quad comparators and have buckets of capacitors. Would the object of the coupling capacitors be to smooth the anode voltages, ie try a 10uF for starters between say Anode A (B,C,D etc) and ground?
Cheers,
Bryan

 

Would the object of the coupling capacitors be to smooth the anode voltages, ie try a 10uF for starters between say Anode A (B,C,D etc) and ground?

The decoupling capacitors are to smooth any spikes that switching devices can introduce on the power supply. We usually use both electrolytic and ceramic capacitors. The ceramic capacitors (0.1uF is commonly used) operate better at higher frequencies where parasitics in electrolytic caps make them less effective.

The most conservative design practices call for one ceramic cap per IC power pin. That's usually sufficient though not always.

 

Thank you Dennis,

With a bit of luck I'll send you a video of it working in the classroom. I think though, that maybe months away.

Yours,

Bryan

 

I think though, that maybe months away.

Many schools here have given up on this year. Now they need to figure out how to handle the missed time. Graduate students, switch to pass fail and grade on what was covered, require them to make up the time, ... Distance learning penalizes the poor (who don't have computers and, in some cases, food), or rural areas that don't have access to broadband. I can't get broadband unless I use 4G - at least my carrier has dropped data overage charges.

 

Could I ask you where is 'here', roughly?

 

Could I ask you where is 'here', roughly?

Pacific Northwest, USA.

The blue interface shows location if you put the mouse over the member name under their avatar. That information used to be displayed; assuming the member gave that information.

 

Must be a lovely neck of the woods.

Ta

 

I apologize for not doing this earlier but the title of this thread needs to be changed to something else that more appropriately reflects the content.
"Simplest question ever asked, but please help anyway!" does nothing for readers, browsers and search engines.
How about:
"How to drive many LEDs for large display clock?"

 

Yes, that is an excellent idea. Sorry about the initial post, it was my first. It got the attention I needed, and I have had a wonderful solution to the problem.

I'll change it if I can.

Bryan

 

Must be a lovely neck of the woods.

Most regions have some redeeming qualities. I live on 5 wooded acres, so sheltering in place is more like being in a forest.

 

Bristol is a beautiful city. Plenty of culture.
This project is one think keeping me occupied in between recording lessons. We're up to the red shift with one year, circular motion with another and SketchUp for a third. Busy!
You Americans use Teams and Google Classroom as a second nature by the look of it. England has some way to catch up.

 

You Americans use Teams and Google Classroom as a second nature by the look of it. England has some way to catch up.

You give the US educational system too much credit. The US school system is a conglomeration of good and bad; mostly bad. Students in rural schools are generally under served and the curriculum is a joke. About the only thing they've added to the high school curriculum in the last 40 years is calculus. The local high school can't even teach programming; I took programming in high school in the early 70's.

Our current secretary of education doesn't believe in the public school system and is trying to damage it as much as she can. Fortunately, she's incompetent.

 

Dennis, I sympathise. I guess that we are of the same vintage, I was born in 1960 (in San Francisco coincidentally).

I was brought up in a practical household, often making or repairing stuff. I have a passion for old British motorbikes and cars and would call myself a jack of all trades (and a master of none). Physics teaching has been mostly a pleasure, but I am saddened by the amazing dumbing down of the syllabus. In my day, calculus and LCR circuits were taught rigorously. Nowadays, even though we have come full circle and it is a lot harder, sometimes 70% is needed to get the highest grade. So sad.
Having said that, the top end is nowadays far far better than it was when I went to University in 1979, but the tail is not catered for at all.
I am watching your country with Trump at the helm, deVos as one of his underlings. I guess (and this might be a dangerous assumption) that you are far enough away from any Republican strongholds that I can safely proclaim that I am shocked by what the USA has become. In Britain, it is now the laughing stock. We are waiting for the next press briefings where his moronic persona becomes even more apparent. I thought covfefe was as low as it could get, but injecting disinfectant? Beggars belief.
Take care, and we look forward to November. Fingers crossed!

 

I want to go back to your original post where you said:

This should be fine for 20 0.02A red leds I thought. So I made a breadboard circuit to try it out.

So basically, you want segments consisting of twenty 0.20 mA LEDS.

Why couldn't you raise the supply voltage to say 48V (common value) and do exactly what you wanted. Put all twenty in series with one resistor and drive from one optocoupler?

Do select the LEDS by Vf so the brightness is about the same. BIN them and maybe add network of resistors that you clip to get the brightness about the same.

 

Hhhhmmm. Now that's an excellent idea! I was barking up the wrong tree, being obsessed with having just one 5V power supply. I could use a 48V one and get 5 from it easily.

dl324 came up with a beautiful solution which would be fun to build. I've ordered the stuff for his now, but will try yours out in the interim.

Thanks!!