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How to click a relay with a low signal?

I need to click a relay when a signal goes low. I have a couple relays on Walter, but they all click when signal goes high. These are pretty straight-forward, just a simple 5v relay, and a 2n222 NPN transistor to click it when a data-level signal goes high. --No Problem

Little circuit help with volt reg.

I am using designing a new PCB for a tidy way of connecting all my 5v doo-dads. It is a pretty basic set-up, 5v- 3a low dropout reg, the obvious caps and some nifty screw terminals. This is all pretty straight forward. Now I also need 3v to replace the (2) AA's in walter's mini ampified speakers. Would it be cool to just use a resistor bridge on this same 5v regulator board to get my 3v?

IF / OR Interrupt? Picaxe...

Hey guys,

I am playing with a 40x2 and the hintsetup and hserinsetup commands also with the flags commands... I would like to interrupt on either a hint signal OR a hserin input NOT both at the same time. It seems that with the various flags conditions, you can stack-up a bunch of stuff that has to be true to interrupt, but there is no "OR" --just a bunch of ANDS


Basically, "if hint1=1 and hint2=1 then inturrupt" but not "if hint1=1 OR hint2=1 then interrupt"...

5V More Current

I've asked this before, but I have pay-pal cash now... Could someone suggest a cheap. simple (limited extra parts) 5v voltage regulator? I'm coming down from 7.2v so I am not coming down much but I do need at least 2  amps --3 amps would be nice too. I did some digikey searching but they have so many options, I was a bit confused.

Final Question:

I need a digikey part # for a good, limited extra-parts, 5v, 2+amps voltage regulator.

 Thanks  Bunches.

Help with 555 circuit.

Well, I have got the 38khz distance sensor working in picaxe form.



Now I am trying to wire-up a stand-alone unit with a 556. Now I know this is a RTF(data sheet) moment and I know the resistor/resistor*cap/2 (or whatever) equation, but the final circuit is still above my head. Are there any of you circuit guys out there that can do a little drawing for me? Maybe with a couple pots for fine adjustment? I plan on the final output going into a picaxe using the pulse-in command.

Thanks in advance.

Experience with PCB's from Sparkfun

The new phone books are here, the new phone books are here!!   ...PCB's actually.


Well, I just got my custom pcb's back from the one-off pcb service from Sparkfun. I gotta say, I am very happy. Granted, it took 3 1/2 weeks to get them but then again, I did get a total of 7 custom boards (with all the bells and whistles) for only 50 bucks including the "set-up" fee and shipping. I used Diptrace to design the boards and the software spit-out all the needed files. Super-simple, cheap, good boards and I'm happy, period.

In this order:

You as a sensor?

Quick question... I want to make sort of a "person switch". Two contacts, where each person would place one finger each on one of the contacts then when these two people would touch each other the circuit is completed. Now, I have not done any preliminary work on this at all --I havn't even measure-thingy'ed myself yet (I would assume we have to be talking some pretty major resistance here).

how do I inverse a number?

Man, I used to know this but tonight, I just can't seem to get it back... If I have a variabe that is coming in at between 0 and 255 and I need it inverted so that 0 is now 255 and 255 is now 0, what is the equasion? This should be so simple, I just can't seem to remember how to do it!

C'mon math Gods, gimme what you got!!

5v regulated but with more current?

Simple question:

Is there a simple cheap upgrade to the good ol' 7805? I need the standard 5v but all of walter's extra boards (i.e. LCD backlights) are starting to get close to, if not over, that 1 amp that the 7805 has to give. I would assume I would never need more than 2, maybe 3 amps.

DC-DC thingies maybe?