Hello everyone!

General question, want to see how you approach a particular problem:

I want to have an option in hardware, between this circuit or that circuit on a printed board. Say to light up an LED, I could use either PA1 or PA2 on a VIA (silly example). How can I decide in hardware how to do that?

Options (that I know of):

1) Solder Jumper. Basically some pads on one side of the board, and I either connect these two pads together, or those two pads together. This option is fairly permanent, unless you get the solderwick out.

2) 2.54 mm Jumper. Have some exposed pins, and place a jumper between them. This option is easily changeable, but I don't like that the tiny little jumper could possibly get lost. I have tiny kids, and tiny toys tend to get lost in tiny mouths!

3) SPDT switch. I use one for switching the power on or off on my board right now. This option is neat, and nothing can get lost, but takes up board space and is (relatively) expensive in comparison to the other two.

I guess there are smaller SPDT's out there like this one:

https://www.mouser.com/ProductDetail/CT ... 7g7Q%3D%3D

But I'm still wondering if there is another option.

I'm looking for a "middle of the road" option. I don't like the permanence of just using solder, but I don't like the fact that tiny jumpers can be lost, and I don't like how many SPDT's are kindof big. Is there something you've seen or used that could be another option?

Thanks for any thoughts!

Chad

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I tend to use .1" (2.54mm) jumpers or dip switches. As Garth shows jumpers do not have to get lost. Dip switched are best for frequent, quick changes but are more expensive both to buy and in terms of layout real estate.

_________________
Bill

First, thank you for reminding me of the correct size: 2.54 mm is what I meant! I edited the first post accordingly.

Second, thank you Garth. Yes, a child consuming a little piece like that won't *really* affect them. But I cannot easily separate 'toys' because I'm using these computers with my daughter on a near daily basis. My 2 yo boy has already ripped the LED off of the computer, I'm sure those radial capacitors look mighty fine as well I'm sure.



Right, you seem to see the point Bill, thank you. The easier to change, the more expensive in money or real estate.

Garth again thank you for the ideas, I'll be considering those as well. I'm willing to hear if someone else has another idea! Thank you all.

Chad

Here's an idea which is at least different: use a trim pot as a switch, by adjusting a pullup or pulldown into a digital gate which can then digitally control the routing of some signal.

Another idea: just build two boards, one each way.

But if you don't plan to change your mind too many times, I'd say a wire link between two pads, which you can snip, or replace.

The little DIP switches are probably good enough for most purposes - they might not have 10000 cycles in them, but you're unlikely to change your mind as often as that.

Thank you Ed!



You know, that is a GREAT idea. It's like a lightbulb turned on, I definitely think I can use this for this very particular situation. Thank you Ed, that was great!



True!



Thank you, good suggestions Ed. I appreciate the feedback. I hope to show results to a lot of my little questions soon in the future.

Chad

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

What if you're unable to decide whether to seek professional help??

Jeff

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Y'all are funny

Attached is picture of the outcome of what I was working on. I have a monochrome display planned, and I was wanting ways change the monochrome color options: Green, Amber, Gray, etc. At first I was thinking of using a jumper to select which one, but the pot trimmer idea was perfect!

So now I'm using pots to adjust the monochrome display to my liking! It won't get super bright because I wanted to keep the 74HC166's output below 25mA (as per the datasheet). But it's now *super* adjustable, much more so than what I was originally planning. This will definitely take up some real estate on the board, but I think it's worth it.

Thank you once again Ed! I know you didn't have this exactly in mind, but it sure was close

And thanks everyone.

Chad

I think there is a jumper for that.

_________________
Bill

Hopefully not the kind that ends in a splat!

_________________
Regards, KM
https://github.com/floobydust

Ouch!!

_________________
Bill

Yea, my bad.... but that is part of the business of professional help.

_________________
Regards, KM
https://github.com/floobydust

Redirecting the "professional help" back to the topic at hand...

I wouldn't worry about exceeding the 25 mA spec. The chips are robust, and also in your favor is the fact that you won't be drawing current continuously. Because the video signal has less than 100% duty cycle, the amount of heat generated in the chip is reduced.

If overdriving the chip isn't sufficient then you could consider adding a simple buffer, more or less as shown below. (Variations are possible. We can discuss those if you decide to go this route. Or, just have at 'er and see what happens!)

-- Jeff

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Thank you Jeff! Yes, BillO had once told me that I could do that. Now you are confirming the same thing. I'll certainly keep this in mind, it would be nice to not worry about 'overdriving' the chip regardless. I'm guessing the capacitor is just a 0.1uF that regulates power to the 2N2222?

Thank you again.

Chad