How many solenoids can be used at once with the Prop-SX?

[tianshi]

I'm thinking of using the Prop-SX to control around 10 solenoids(6vdc each). Not all the solenoids will need to move at once, maybe 2-3 will need to be powered at the same time. Is this possible with the Prop?
   Also, is the Prop-SX camera compatible? Or is there some way to get it to be camera compatible?

[JonnyMac]

The ULN2803 that is used in the Prop-SX has specific current limitations based on the number of active outputs.  What this means is that it's not enough to know how many outputs are on at a given time, but what the current draw per output is.  Do you have a spec on the solenoid?

I don't know what you mean by "camera compatible."

[tianshi]

well, I'm still not sure on what solenoid to use yet. I don't need very much force, so I'd get the lowest grade of solenoid. But I still need a solenoid with enough length, so something close to this:
http://www.solenoidcity.com/solenoid/tubular/s-16-50hp1.htm
As for the camera, I guess its something more of a color sensor:
http://www.parallax.com/Store/Sensors/ColorLight/tabid/175/CategoryID/50/List/0/Level/a/ProductID/429/Default.aspx?SortField=ProductName%2cProductName
can this be attached to Prop-SX?
If i only need 3 outputs on at the same time, what is the max current draw per output?

[JonnyMac]

I actually called that company since they're near me in the Valley -- was an interesting call. 

If you look at that chart you'll see a resistance column for each wire size; take that number and divide it into your voltage -- that will tell you much current that the coil uses (we don't have to worry about inrush).  To calculate how much current a coil will use, plug the numbers into this formula:

  (Input voltage - 1.3) / Coil resistance

Let's say you're using a 12-volt supply and you have the coil made with #34 wire.  You get:

  (12 - 1.3) / 65.2 = 164 mA

At 164 mA you can safely run up to six of these solenoids without over-stressing the ULN.

Yes, you can connect that TAOS color sensor (it is not a camera) to the Prop-SX.

[tianshi]

thanks! I'll look into it!