Specifications

1
BooBox FlexMax FI-216 Operating Manual - page 5
2
Solid-State Outputs
About the Solid-State Outputs
The solid-state outputs are ideal for reliably controlling relays and solenoids. They cannot be used to directly
control A.C. powered or contact-closure devices like a relay can. However, unlike relays, they have no moving
parts that will wear out over time. They also have feedback suppression diodes built-in to absorb the nasty
noise relays and solenoids release the moment they are turned off.
To use the solid-state outputs reliably you must be mindful of their current limitations. Each output can handle
500mA of current regardless of the supply voltage, this calculates to 6 watts at 12 volts, or 12 watts at 24 volts.
This is why we recommend 24 volt supplies, you will be able to use much larger solenoids without exceeding
the 500mA limit.
Internal Fuses
In addition to the 500mA per output limit, there are also two internal fuses, one for outputs 1-8, and one for
outputs 9-16. These fuses will temporarily open if the sum of the current flowing through either set of outputs is
around 1.1A for too long. The fuse will automatically reset once the excessive draw has been removed. This
may sound like a limitation, but not really. Most solenoids draw about 5 watts on average, at 24 volts that’s
210mA per solenoid. So four valves could be left on continuously without fear of overloading.
Do Not Short The Outputs!
The internal fuses will protect the solid-state driver chips from being overloaded, but they are not fast enough to
protect them from direct shorts. Double-check your wiring before you power up. If you see a small puff of
smoke or smell something nasty, you may need a new driver chip.
Replacing the Solid-State Driver Chip
If some or all of the outputs are no longer working, or they are all on no matter what you do, the solid-state
driver chip likely needs to be replaced.
Buying a New Chip
The driver chip used in the BooBox is a very popular chip used by many manufacturers. We carry them on our
website, but they will almost certainly be available at a local electronic component supplier if you’re in a jam.
You can also purchase them from online suppliers like Digi-Key and Mouser.
The chip’s part number is ULN2803A. Various manufacturers make compatible parts with almost identical part
numbers, although there may be a few more letters after the A. As long as the chip package is DIP and it looks
like the picture below, it will almost certainly work just fine.
Replacing the Solid-State Driver Chip
Replacing the chip is a somewhat delicate process. The best way to learn how to do it correctly is to watch the
video on our website. Search for driver chip in the search box and click on the first hit to see the product details
and video.