Lighting question--common grounds?

[jgoldader]

Hi folks,

I'm trying to light a PL Klingon D-7. The lighting consists of two parts:

a) blinkers (w/ 555 blinker circuit board that will live in the base) and

b) three sets of always-on LEDs that will be wired in parallel with dropping resistors selected to make sure the resistances match.

I'll be using a 9V battery.

I knew I'd need two switches, and I've got them, but I realize I'll need two batteries as well--I don't know how to match the resistance of the blinker circuit and the always-on LEDs.

I would like to provide power to the model using a stereo miniplug, so I've got three wires to work with. Ideally, I'd have four wires, of course.

Is it possible to put the +V from the two batteries in common, with the ground wires from each set of LEDs (the blinkies and always-ons) switched? I believe that should be okay.

Worse case scenario is I hardwire a 4th wire into the model, but that would mean I can't remove it from the stand.

Thanks for your advice!

Jeff

[en'til Zog]

How many LEDs are you blinkifying and what colors are they? Sometimes the simplest approach is using one self blinking LED in series with a couple of other LEDs and the SB LED blinks all of 'em.

What color are the 3 non-blinking LEDs? Some LEDs are low enough in voltage needs that you can put 3 in series with one dropping resistor. F'r instance, 3 RED LEDs at 1.9 volts need 5.7 volts if wired as a series string, leaving 2.3 volts to drop, using a 9 volt battery. Using 3 LEDs that need 3 volts each lets you put 'em all in series and use NO dropping resistor.

As always, I recommend building all the blinkificaion stuff on an experimenters bread board first, leave it running, and see how it works.

HTH

[DLMatthys]

Jeff

Zog has a good point about your desired operating voltage. Bring it down to the voltages that your LEDs need which is mostly 2.5 volts for color LEDs and 3.5 for white. Lowering it will also still operate the 555 IC chip circuit. Probably at a lower and more desired speed of blinkin'.

[jgoldader]

How many LEDs are you blinkifying and what colors are they? Sometimes the simplest approach is using one self blinking LED in series with a couple of other LEDs and the SB LED blinks all of 'em.

What color are the 3 non-blinking LEDs? Some LEDs are low enough in voltage needs that you can put 3 in series with one dropping resistor. F'r instance, 3 RED LEDs at 1.9 volts need 5.7 volts if wired as a series string, leaving 2.3 volts to drop, using a 9 volt battery. Using 3 LEDs that need 3 volts each lets you put 'em all in series and use NO dropping resistor.

As always, I recommend building all the blinkificaion stuff on an experimenters bread board first, leave it running, and see how it works.

HTH

I breadboarded the blinking part, then cobbled the circuit together on a PC board, then, ashamed of my poor skills, ordered a couple of Don's boards...

Here's what I'm working with, in more detail. Some of the LEDs are mounted in the model already, so I will have to find some way to make this work.

1) Blinking lights--two sets of red+amber in series, to be lit in parallel off a 555 driver as strobes; they work properly at 9V

2) Constant on (all blues)--three sets of two blues in series; would like to illuminate these all in parallel with each other

Ideally, I could do this with two switches.

I experimented a little after making my first post. I can power one set of blues and the 555 circuit in parallel off a single 9V, but there's a current drop in the blues when the blinky is in the "on" state (which makes sense to me, as some current has to flow through the strobing LEDs, leaving less for the blues).

Maybe I bit off more than I could chew for this one, eh?

In my defense--the 555 circuit works, the blues work, the only thing I fouled up on was getting power to the things.

Thanks again,
Jeff

[jgoldader]

Okay, I managed to solve my own problem. I ended up ditching the stereo minijack I was going to use for power and will use a pair of 8-pin IC sockets, one in a rod coming up from the base, the other epoxied into the D-7 hull. This gives me four wire pairs, that's plenty for the project. I will power the lights with two 9V batteries and two switches.

Thanks to those who offered advice!

Jeff

[en'til Zog]

Glad to help! Even gladder to "see" you hacking away and solving your own problem! (With just a little bit of help from the side maybe.)

[jgoldader]

It works! It actually works! I finished the connections tonight, and it worked like a charm.

I'll post a full report to the Bench tomorrow, but now I'm just gonna relax. Earned it, I have.

Thanks again to everybody for your help & encouragement!

Jeff