help with project with map & LED's

Don't worry lately I was off by 2x10^3 due to wrong conversion of Quads and BTUs, cazzo!

The SCRs will handle the current with 1K resistors as the limiters. With 2A current a possibility, you want to mount the SCRs on heat sinks. Also, make sure your relay contacts can handle at least 2 amps.

Ed

The simplest solution is to use an array of 8 radio buttons or a tap changer. If you want an electronic solution I'd propose using an 8 input priority encoder like 74hc148, a 4bit latch and a 3 to 8 decoder like 74hc138. The 74hc148 has an output that changes if any of the inputs is active. This output latches the 3 bit address of the highest active input. These 3bit are decoded by the 74hc138. Of course you will need buffers to driver the leds.

You should probably run them in series strings. You'd need more volts, but that shouldn't be a problem, since you very probably are using the mains supply anyway. If you use series strings of, say, 10 LEDs, that'd be a Vf of 12 volts or so (depending on the VF of the leds, of course), at only

20 ma, for a total of 4 A, if my arithmetic is correct. Or, you could use even longer strings, depending on how many mines you have per set.

Good Luck! Rich

Use peanut butter. Mice don't really like cheese, they just eat it because they're starving, which makes the bait pretty ineffective if there's other mouse food around.

Or capture them live and take them to the pet shop to be sold for snake food. ;-)

Peanut butter is also good bait for a live trap. :-)

Good Luck! Rich

Or, better yet, push-on, push-off buttons. ;-)

Cheers! Rich

hey that's neat!

have you considered this.

+12 -+--. .--------[1K]--------+---------+---{{{-----+ | \\| / | | | | ~~T~~ [LED] [LED] [LED] | | | | | | | [SCR1] [SCR2] [SCR8] | | Pb1 /| /| /| | | ___ | | | | | | `-----------+--o o---[330]--+ +---------+---{{{-----+---+ | | | | | | | | +--->|---------+ | | | | | D1 | | | | | | Pb2 | | | | | | ___ | | | | | +--o o---[330]------------+ | | | | | | | | | | +--->|---------+ | | | | D2 | | | ((( {{{ {{{ {{{ {{{ | | | | | | | Pb8 | | | | | ___ | | | | +--o o---[330]------------------{{{---+ | | | | | | +--->|---------+ | | D8 | | | | | | || | | `-->|--+--||--------------+ | | ||100pF | | | | | [1K] [10K] | | | | Gnd --------------+------------------+-----------{{{---------+

I think the original poster wanted to control more than one LED they could be wired in series and a higher voltage used.

4148's are ok for upto 200mA, they'd probably work everywhere

Bye. Jasen

I like your idea.

Yes, multiple LEDs. Each SCR can control 4 amps, so he can wire as many LEDs as he needs to each. The schematic didn't show multiples, for simplicity in drawing, but it was mentioned in the text. The problem with going in series is not electronic - it's logic. Only those mines that have the exact same minerals can be in the series string, and if you make a mistake, you have to re-design the LED circuit for that string and for some other string. When you make a mistake with the single LED, it is a simple fix - just connect it & its resistor to a different spot through a steering diode. It doesn't affect other LEDs.

Good point - makes more sense to use the same diode throughout. Somehow I had it (erroneously) in mind that the 1N4148 was good for 75 mA.

Ed