■ FIGURE 5
you can help, it truly would be
appreciated. It will be used to drive
46 double LED strips similar to
“Hyperion R-lite Systems.”
— Frank Lemon
■ FIGURE 6
POWER
SUPPLY
QI need a 120 VAC to 7. 6 VDC 3A
regulated power
supply, and have
been unable to find
a schematic to
construct such. If
AThe power supply could be designed using a standard transformer, or as a switching supply using a
ferrite core. Since I don’t know of
any source for ferrite cores for hobby
use — and RadioShack is pretty much
out of the hobby electronics business
— I will go with a standard
transformer design (see Figure 7).
Hammond transformer 183J16 has
an output when wired in parallel of 8
VRMS at 3. 8 amps. The full wave
rectified voltage will be about 10
volts which is enough headroom for
a 7. 6 VDC regulator. The filter cap
needs to keep the ripple below one
volt so the regulator doesn’t run out
of headroom. Using the relation: dV
= I*d T/C where I = 3A and d T =
8.3mS, I calculate C = 24.9 millifarads
= 25,000 µF (minimum). The LM317
is rated at one amp, so a current
boost is needed and is provided by
Q2. When the LM317 current
exceeds 10 mA, Q2 gets turned on
to provide the majority of current.
■ FIGURE 7
24
July 2010
