Adjustable Output Positive Voltage Power-Supply Kit
(Adj. output 1.25V to 24 VDC)
is an electronics
(kit) that allows you to connect up to 30V AC or DC on one side of the board
and get adjustable VDC regulated on the other side. Every lab should
have a few of these boards handy. The boards will allow you to
easily power all your analog components (i.e. op-amp). The Terminal Block TB
connector is included and makes it easy to use.
Board With optional
operation of the adjusted voltage regulator board
bridge D1-D4, together with the capacitor C1, will convert input AC voltage to DC
Voltage (See below kit drawing). Additionally, the diode bridge ensures that the
polarity of the bridge output remains the same regardless of the
input voltage polarity. It's what we call "dummy-proof." Let's say,
for example, the board is powered by a 24V battery, the output polarity remains
the same no matter how you connect the power to the board's
other side of the diodes bridge drives the voltage regulator U1.
The adjustable voltage regulator is the main component of this kit (regulator). Usually
having three legs, it converts
varying input voltages of > 24 and up to about 30 VDC or VAC, and produces a constant regulated output
voltage base on your settings (adjustment via P1).
positive voltage regulator
is available in a variety of packages for different outputs and max
current driver. The most common part numbers
of the adjustable voltage regulator
is LM317 for an output of up to 1A with 1.25
to 24VDC output. This
monolithic integrated circuit (IC), is an adjustable 3-terminal
positive voltage regulator designed to supply more than 1A of
load current with an output voltage adjustable over a 1.35 to
30V. The LM338 should be use with when circuit require output of up to
3A. and the the LM138 for up to 5A. See more info below. Heat sinking block is usually require when pulling current >
400mA (optional). Heat sink are manly manufacture from Aluminum
material. One can use our die-cast aluminum
enclosure, for both heat-sink device and enclosure to house its power supply
The LM317, LM338 series
of adjustable voltage regulators are designed for positive input.
The adjustable regulator LM317 typically has the ability to drive currents up to 1A.
Application requirements only up to 150mA, LM317 in a TO-92 packaging
can be used. Ask our sales engineers for more details.
LM317 series of adjustable 3-terminal positive voltage
regulators is capable of supplying in excess of 1A over a 1.25V
to 30V output range. They are exceptionally easy to use and
require only two external resistors to set the output voltage.
Further, both line and load regulations are better than standard
fixed regulators. Also, the LM317 is packaged in standard
transistor packages (TO-220 and T-92) that are easily mounted
addition to higher performance than fixed regulators, the LM317
series offers full overload protection available only in IC's.
Included on the chip are current limit, thermal overload
protection and safe area protection. All overload protection
circuitry remains fully functional even if the adjustment
terminal is disconnected.
no capacitors are needed unless the device is situated more than
6 inches from the input filter capacitors in which case an input
bypass is needed. We calculated a capacitor (C1) of 47uF for our
input filter. It will be sufficient for both 50 and 60 HZ lines
voltage. An optional output capacitor (C3) can be added to
improve transient response and stabilization. In environment
(industrial etc.) with high frequencies additional cap
(C4) is require see text for more details. The adjustment
terminal can be bypassed to achieve very high ripple rejection
ratios, which are difficult to achieve with standard 3-terminal
regulators. Adding 10uF across the ADJ pin (leg) will add
stability when fast voltage swings is requires. Furthermore this
cap (C2) is used as a low past filter (L.P.F. or LPF) and will
alienate any frequency of above 6Hz at minimum output voltage, (F=1/2*PI*RC).
is useful in a wide variety of other applications. Since the
regulator is "floating" and sees only the
input-to-output differential voltage, supplies of several
hundred volts can be regulated as long as the maximum input to
output differential is not exceeded, i.e., avoid
short-circuiting the output. Please be advised that our kit
design for a maximum voltage of 30V. Also, it makes an
especially simple adjustable switching regulator, a programmable
output regulator, or by connecting a fixed resistor between the
adjustment pin and output.
applications requiring greater output current, see LM338 series
(rated up to about 3A) and LM138 series (rated up to about 5A)
of the Features of the LM317 include: 1% output voltage tolerance, max. 0.01%/V line
regulation, max 1A output current, adjustable output down to
1.25V, current limit constant with temperature, 80 dB ripple
rejection, output is short-circuit protected.
above, the component has three legs: Input leg which can hold up to
36VDC (we recommend not to exceed 30V), Adjustable leg (ADJ) and an output leg with the regulator's
voltage. For maximum voltage regulation, adding capacitors C3
and C4 in parallel between the ground and the output is usually
recommended. C4 a 0.1MF capacitor is used. This eliminates any high frequency AC
voltage that could otherwise combine with the output voltage.
See below circuit diagram for the kit.
protection diode D5 added to prevent C3, C4 combination from
discharging thru the regulator during an input short circuit.
The diode D6 protects against capacitor C2 discharging thru the
regulator during an input short circuit. Therefore the
combination diode D5, D6 prevents the C2 (adj. cap) from
discharging thru the regulator during an input short circuit.
As a general rule the input voltage should be limited to 2 to 3 volts
above the output maximum voltage. The LM317 series can handle up to 36
volts input, be advised that the power difference between the input
and output appears as heat. If the input voltage is
unnecessarily high, the regulator will overheat. Unless
sufficient heat dissipation is provided through heat sinking, the regulator will shut
Therefore, you will need to mount a heat-sink on
the regulator that is capable of dissipating the access heat
produced. please also note, that the metal body of the LM317
(TO-220 package) is the connected internally to the output leg
of the IC.
Replace the 1N40017 diode with 1N5006 and using LM338 (up to 3A)
see above text for more details. The PCB is design to fit both
diodes (extra holes locations and size to accommodated different
diode sizes). For you convenient, we carry inventory of the
voltage is set by two resistors ratio R1 and P1 connected as
shown above. The voltage across R1 is a constant 1.25 volts and
the adjustment terminal current is less than 100uA. The output
voltage can be closely approximated from V+ = 1.25 * (1+(P1/R1))
which ignores the adjustment terminal current but will be close
if the current through R1 and P1 is many times greater. A
minimum load of about 10mA is required, so the value for R1 can
be selected to drop 1.25 volts at 10mA or 120 ohms to be on the
safe side, we recommend resistor of about 240 ohms. Something
less than 120 ohms can be used to insure the minimum current is
greater than 10mA.
power is shut off to the regulator, the output voltage should
fall faster than the input. In case it doesn't, a diode D5
connected across the IC input and the output terminals protect
the regulator from possible reverse voltages. A 47uF
electrolytic capacitor across the output improves transient
response, and a small 0.1uF capacitor is recommended across the
output (see above text). The power transformer should be large
enough so that the regulator input voltage remains 2 to 3 volts
above the output at full load.
a particular output voltage (V+), you can replace resistor R1
and trimmer P1 combination with 1% resistors. For example use R1
= 340 ohms, and replace P1 with resistor value of 3.74K ohms,
both in 1% tolerance. You will get very close to 15VDC output
voltage. Ideally for single rail voltage require by many
operational amplifiers (Op-AMP). Use R1 = 249 ohms and P1 = 750
ohms and get 5VDC output voltage, ideally for all your TTL and
CMOS power needs.
4 pre-set voltages simply by a pressing a push button (switch),
see schematic below. Simply connect Ax and GND to point A and B
on the main PCB respectively. The switching mechanism will
replace P1 with 4 new predetermine voltages
for 6 predetermine voltages the see sch. below using 6 positions
heat-sink (if needed). Additionally, Please
heat-sink, Din-Rail mounting clip, wires and transformer are sold as
Shown above high-current settings
adj. power supply
board with heat-sink
and wires options.
our line of transformers click