EZ-8 power

[dvdbob]

Jon,

Can I replace a (2)AA battery pack with the V+ connection from the EZ-8?

[gadget-evilusions]

2 AA would be 3V, and the V+ connection on the EZ-8, if your using one of the EFX-TEK power supplies would be 12vdc.

[JonnyMac]

Yes, with care.  Do not connect the positive side of your battery pack to V+.

You can connect the ground side of the battery pack to the GND terminal, the positive side of the battery pack to the positive side of the device, then the ground side of the device to the ChX terminal of your choice.  Keep in mind, though, that there is about a one-volt drop across the ULN -- you may notice this, depending on the device.

[BigRez]

Isn't dvdbob asking to get rid of the battery pack and replace it with poser supplied by the prop-1 ?  For example, perhaps to trigger an always-on device that requires 3vdc.

If this is the case, couldn't he pull the 5vdc from one of the pins and reduce that to 3vdc using a resistor or voltage regulator or something like that?  (There I go again... showing my electronic ignorance. :)

I've got the same thing I'd like to do this year for one of last year's props...  The "sound" card is a carcas from a broken wall decoration.  Powered by 2AA batteries and triggered by movement.  I kept the batteries in the prop and placed the motion sensor next to the prop's head to that when it popped up, the sound started.  I had to keep the card on all the time though and would like to replace the batteries (and the motion trigger, but that's a different thread.)

[JonnyMac]

I think you're right, Bigrez, I took the question as controlling a 3v battery pack from V+.  My mistake.

DvdBob: Are you comfortable with electronics? (i.e., building a regulator circuit)  If yes, you could build a 3v regulator circuit (I'd actually bump it to 4v to overcome the ULN drop as I discussed earlier). 

[dvdbob]

Bigrez - Yes, precisely.  I'm taking an off the shelf decoration and would like to integrate it into my EZ-8 experience (Lighting Eyes with the controller) when the prop is triggered.

Jon - Yes, i'm comfortable building the electronics (if I have some instructions and references).  I will review and investigate. Thanks, Bob.

[JonnyMac]

Do you have any idea how much current (at about 3v that you need?).  If its less than 500mA, what you could do -- as BigRez suggested -- is pull +5v from the TTL header.  Run this through a 1N4001 diode (anode side to +5v) to drop the voltage to 4.3v.  The ~1v drop through the ULN (when switching on) will provide just a smidge over 3v to your device.  Does this make sense?

Let me suggest you use a meter between the cathode of the 1N4001 and the ChX terminal (when active) to make sure things are working as intended.  You can add another diode for an additional 0.7v drop if needed.  Just make sure to use a 1N4001 (or higher, 1N4002, etc.) to handle the current.

[BigRez]

I'm not sure how much current my device draws.  It's tiny and only has unamplified sound so I've got to believe it's less than 500mA.

Trying to understand the connections (assuming pin5)...  anode side of the diode to P5.W, cathode side to device (+), device (-) to P5.B.  Is this correct?

And then, I have a bunch of 1N4148 diodes from another project here in the forums that I built just for fun.  (My wife bought the 50 pack rather than the 5 pack because they were a "better deal."  ::) ) Can the 1N4148 diodes be used instead of the 1N4001?

[JonnyMac]

Nope, you cannot use the 1N4148 diodes; the are tiny little signal diodes and will probably pop.  Even at RadioShack the 1N4001 will only set you back about a buck, and it can handle a full amp so you know you're safe.

Here's a schematic for clarity:

[BigRez]

Perfect!  Thanks Jon.  I'll run down and pick 'em up so I don't wind up with too many extras.  ;)