replacing a 9 v battery with an adapter?

paradrape

hi,

i'm trying to do something simple.

I bought a 9V adapter from Radioshack to replace the 9v running though my relay on my Basic stamp.

It's a 9V 1500mA International - cat. no. 273-1711

I cut the chord and spliced it into a 9v...um the thing that attaches to the battery (red and black wires)

i'm running the power into a piece of Flexinol wire which contracts and expands on a script from the BS.

BUT...when i run the script and the 9v adapter is plugged in all that happens is a slight spasm in the wire. it does not fullly expand and contract the way it should and the way it does when i have a battery attached.

what's wrong? too many (too few) mA? Should i get a 300 mA adapter?

how should i attach it to properly replace the battery? which wire goes with the red and which with the black? I've heard the half of the adapter cord·with the writing on it goes with the red...

thanks...

kenwtn

Check the adapter end with volt ohm meter make sure you have the correct connection or use a led.

Mike Green

Buy a multimeter at RadioShack before you go any further. They have some as cheap as $10. You don't need to spend more than $20 unless you like fancy stuff. Measure the voltage at the battery clip that you attached to the AC adapter. You should get roughly 9V. Make absolutely sure that the polarity is the same as a 9V battery so the red lead is touching the same shape clip on the adapter as on the battery to get a +9V reading. The 1500mA rating of the adapter should be more than enough. Most 9V batteries won't supply that kind of current

allanlane5

I think "Flexinol" wire takes quite a lot of current -- how are you switching this current? You probably need another device besides the BS2 -- like a transistor -- to switch enough current.

erco

I bet you mean RS 273-1771. This should work fine. Probably one the Shack's new breed of lightweight, transformerless adapters regulated to 9 volts. But it is an international multivoltage unit (you did·set it on 120 volts, not 240 V, right?) and may have other issues.·It should hold 9 volts out to the rated current of 1.5 amps. That's a LOT of current, much·more than any 9V battery can put out for more than 2 seconds. Allan's right, flexinol & nitinol take lots of current. Sounds like you're switching·a relay with your Stamp (reed relay direct from an I/O pin, or coil relay through a transistor?) and using that to switch your 9 volt supply to your flexinol. Should work better & faster than a 9V battery if hooked up properly.·Per Mike, get·a digital meter ($3 at a Harbor Freight sale) and check voltages everywhere. Also, try a brief direct connection from your AC adapter to your flexinol. That should kick hard instantly. If it doesn't, your adapter may be bad. Reviews on the RS site say the plug is fragile and easily broken, FYI.

Post a schematic if you can't git 'er done...

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·"If you build it, they will come."

David H.

Paradrape,
I made an adapter that plugs onto the 9V connector on the Board of Education. Like Mike mentioned, make sure the polarity is correct. I messed up the polarity the first time I did this. Because I found out that I had to hook the Positive line from my power supply, to the BLACK wire of the connector, and the Negative line to the RED wire. Because when you plug it into the connector on the board, the polarity gets reversed.

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David


There are 10 types of people in this world,...
Those that understand binary numbers, and those that don't!!!