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Topic: Seeking an alternative to transistor (Read 1 time) previous topic - next topic


I'm working on a project that employs the Miga NanoMuscle.  The first iteration only uses one, and the HIGH/LOW commands were being handled by a 2N4401NPN transistor from RadioShack.  I'm ready to step it up, and employ four NanoMuscles at once.

My question is: Is there a suitable single-component alternative to handling varying HIGH/LOW commands for each individual NanoMuscle?

Thanks!   :)


Can you provide a link to information on the "NanoMuscle" please?
[ I won't respond to messages, use the forum please ]


Apr 26, 2012, 07:38 pm Last Edit: Apr 26, 2012, 07:40 pm by khansen3 Reason: 1
Sure thing! http://www.sparkfun.com/products/8782

Miga NanoMuscle

sku: ROB-08782

Description: Another great linear actuator from Miga Motors. The NM70 is a very small electric actuator that utilizes Shape Memory Alloy (SMA) with a 4.0mm stroke when exposed to 3.5V and 410mA.

Sorry for leaving that out.
The 2N4401 NPN is rated at 600mA (0.6A) 40V


http://www.ti.com/lit/ds/symlink/uln2803a.pdf  is what you want.


Previous poster beat me to it - yes Darlington array can handle the 410mA and will help drop 5V down to the 3.5V.  Just be careful about total power dissipation if powering 4 of these devices (Darlingtons saturate at a volt or more).  perhaps one of those little stick-on heatsinks for ICs would be useful.
[ I won't respond to messages, use the forum please ]


thanks a lot guys.  is there a way to prevent power dissipation?  i'm starting to think that i should just stick with four transistors.


i'm starting to think that i should just stick with four transistors.

I think you should because you can't have all 4 on at once with this chip, see:-

is there a way to prevent power dissipation?

No but you can minimise it by having a component that does not drop as much voltage when it is on. A good logic level FET will not dissipate as much power.


You could use relays.  I just ordered some from futurlec. Here is a link to the ones they have:

They have 5 volts relays that you can drive direct from the pins on the arduino.  Make sure that you don't draw more current then the arduino will source, check the data sheet and use ohms law if you didn't know that.  Or get a ruggedduino and it will put out 500ma per pin!


is there a way to prevent power dissipation?

Yes, use a logic level N-channel MOSFET to switch the low side. You want logic level as it won't require more than 5v to turn on fully.
A FET with a low Rds(on) will dissipate much less that a transistor, you can calculate dissipation with P = V*V/R.

If you want SMD, the IRLML2402 is a nice part in SOT23. http://www.irf.com/product-info/datasheets/data/irlml2402.pdf

For through hole parts, Digikey's parametric search comes up with many choices, the first one is good for 600mA at 5v gate, second one is quite beefy with a really low Rds(on):


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