13V/2A PSU For Handheld Rigs

This compact 13-V/2-A power supply for ham radio rigs and other VHF/UHF portable PMRs
is based on the STR2012/13 voltage regulator IC from Sanken Electric
Co. Many power supplies for handheld amateur radio rigs are based on the
LM317, LM350 or even the good old LM723. Unfortunately, these
regulators are invariably associated with a fair number of external
components, while we should also consider design factors like total
power dissipation and input voltage range. The STR
is a hybrid power IC containing a switch-mode power supply. It supplies
a fixed output voltage and accepts relatively high input voltages.

Another advantage is its relatively high power dissipation rating. The 5-pin STR
is available for 5.1 V, 12 V, 13 V, 15 V and 24 V at an output current
rating of 2 A. Here, the STR2012 and STR2013 are suggested for output
voltages of 12 V or 13 V respectively. The normal operating voltage of
most handhelds being between 12.6 V and 13.8 V, the STR1303 will be the
preferred device in most cases. A high-speed crowbar circuit is added to
the regulator output. Thyristor Th1 (a TIC106 or 2N4442) is triggered
when the output voltage rises above the zener voltage of D2, that is, 15
volts (approximately). When this happens, the thyristor short-circuits
the supply output, protecting the radio against over voltage and blowing
fuse F1.


Circuit diagram

Diode D1 acts as a reverse polarity protection, also in combination with fuse F1. To allow for its dissipated heat, the STR
regulator should be mounted on a heatsink. Efficiency will be around
80%, with ripple rejection at a comfortable 45 dB. The raw input voltage
to the regulator should be in the range 18 to 35 V. The coil, L1, may
be selected from the range produced by New-port. The type 1430430 is
suggested. If difficult to obtain, then an ordinary triac suppressor
type may be used instead.

Note, however, that the inductance of these coils is usually just
100µH, so you have to count the number of turns and add another 0.7
times that number to arrive at about 300 µH. Finally, keep the wire
between pin 3 of the STR and ground as short
as possible, and connect at least the negative terminals of C1 and C3 to
this point to give a ‘star’ type ground connection.


Rugged PSU For Ham Radio Transceivers

This rugged power supply
is based on the popular LM338 3-pin voltage regulator. The LM338 is
capable of supplying 5 A over an output voltage range of 1.2 V to 32 V
with all standard protections like overload, thermal shutdown,
over-current, internal limit, etc., built in. In this power supply, some
extra protections have been added to make it particularly suitable for
use with low to medium-power portable and mobile VHF/UHF
(ham) and 27 MHz transceivers. Diodes D4 and D5 provide a discharge
path for capacitors C1 and C2. Diode D8 protects the supply against
reverse polarity being applied to the output terminals. Capacitor C1
assists in RF decoupling and also increases the ripple rejection from 60
dB to about 86 dB.


Circuit diagram

If junction R1-R2 is not grounded by switch S1A, transistor T2
starts to conduct, causing the regulator to switch to zener diode D7 for
its reference voltage (13 V). The PSU output voltage will then be 12.3 V. Normally, T2 will be off, however, and the PSU output voltage is then about 8.8 V. The high/low switch is useful to control the RF power level of modern VHF/UHF
handhelds. Transistor T1, a p-n-p type BC557, acts as a blown-fuse
sensor. When fuse F1 melts, T1 starts to conduct, causing LED D6 to light. If, for whatever reason, the PSU output voltage exceeds about 15 V, thyristor THR1 is triggered (typically in less than a microsecond).

Such a high-speed ‘crowbar’ may look like a drastic measure, but
remember that this kind of protection is required by digital ICs that
will not stand much overvoltage. The crowbar, when actuated, will
faithfully destroy fuse F1 rather than allow the PSU to destroy expensive ICs. The two LEDs
on the S1B contacts not only act as ‘high/low’ indicators but also as
power-on indicators which are turned off when the mains voltage drops
below about 160 V. If you envisage ‘heavy-duty’ use of the PSU,
then voltage regulator IC1 should be mounted on as large a heatsink as
you can get. The minimum we’d say is an SK129 heatsink from Fischer (Dau


Upgrade Your USB Hub

Problems can arise with USB
hubs that are powered from a PC when gadgets plugged into them draw too
much current. This is often the case with devices fitted with USB cables that are too long or too thin, causing voltage drop. There’s no need to scrap your old USB hub, however, if you upgrade it using this little circuit and an external power supply. Just cut the 5-V power wire of the USB
cable inside the hub and solder a diode (D1) in the pass-through
direction. Now connect the 5 V wire from the external power supply to
the cathode of this diode. D1 prevents any current from the power supply
from flowing back into the PC.

Upgrade Your USB Hub

Upgrade Your USB Hub


Ni-MH Ni-Cd Adjustable Constant Current Charger

Ni Cd Ni MH Adjustable Constant Current Battery Charger

Ni-Cd Ni-MH Adjustable Constant Current Battery Charger Circuit

This is a Adjustable Constant Current Ni-MH or Ni-Cd battery charger circuit. It can be used to get a constant current power supply. Here is the schematic diagram of the circuit:

Ni MH Ni Cd Adjustable Constant Current Battery Charger circuit



500Ω Preset






This circuit can be adjusted to any value from a few milliamp to about 500mA. The max current is 500mA because it is the limit of the BC140 transistor in the current-limiting part of the circuit.

The input voltage has to be 5.25v above the required output voltage, because of 1.25v across the current-limiting section and Approximately 4v is dropped across the regulator.  The LM317 3-terminal regulator will need to be heatsinked.

LM317 pin configuration

the LM series of regulator is suitable for this circuit because they have a voltage differential of 1.25v between “adj” and “out” terminals.

BC140 transistor pin Configuration pinout

For example, to charge 4 Ni-Cad cells, just connect them to the output and adjust the 500Ω preset until the required charge-current is obtained. The charger will charge 4 Ni-Cad cells at the same current. But, don’t forget to turn off the charger before the cells are fully charged or the battery will be over-charged.

LM317 Adjustable Constant Current Charger
Ni Cd Ni MH Adjustable Constant Current Battery Charger


LM317 Calculator

LM 317 calculator

LM317 Calculator or LM317 Toolkit Software

Program to calculate the resistance at a LM317 / LM117.

Lm317 calculator software lm317 toolkit download

LM317 toolkit software is completely free, fully functional and easy to use. It runs under Microsoft Windows NT, 2000, XP and Vista.



Power Guard

Power Guard Under and Over Voltage Protector

Under and Over Voltage Protector

A few circuits on under/over voltage protection have appeared recently in EFY. But this circuit is simple, very easy to construct and inexpensive. It can be added to existing stabilisers, in which case DC power supply can be taken from the original stabiliser circuit and only a few additional components, including one relay, are required to make the circuit.

Power Guard Under and Over Voltage Protector circuit




10KΩ 1/2W

1000µF 25V

250µF 25V



HL 100

HL 100

12V 450Ω

Bz 148

Bz 148

BY 126 × 4

12V 500mA

When supply voltage is within limit. T2 conducting and T1 is in a non-conducting state. At low voltage, zener Z2 will not breakdown and T2 will not conduct, which results in de-energising the relay. This adjustment is done by adjusting VR2.

At high voltage, zener Z1 will breakdown and T1 will go in conducting state and the relay will de-energise. This adjustment is done by adjusting VR1. Normally-open contact of the relay is used in control circuit. Red LED gives high low voltage cut-off  indication.


HV2405E transformerless stabilizer

Using HV2405E chip, manufactured by Harris, along with a few external components connected like in this circuit diagram can be achieved a voltage stabilizer without a voltage transformer. Using HV2405E chip can get a 5 + 24V stabilized voltage directly from the mains AC 100 260V.Peak output current of stabilizer is 50 mA.
Integrated circuit contains a preregulator ensuring charge of C2 a sufficient capacity at the beginning of each voltage network. Charging continues until the capacitor voltage has reached a desired value plus 6 V.

When it reaches this state, C2 provides the necessary voltage to series regulator also contained by integrated circuit. Output of this regulator is adjustable, between 5 V and 24 V, with P1 and is available at pin 6.

Load current will discharge a C2 capacitor, but the preregulator ensure its proper recharge during each period of tension network.

Circuit Diagram: 

HV2405E transformerless stabilizer circuit


DC-DC Multi-Chip Module Family

DC-DC Multi-Chip Module Family

DC to DC module Family

New energy standards, combined with new system specifications for blade servers, high performance notebooks, gaming consoles and POL modules, are driving the requirements for better efficiency, higher current, higher switching frequency and increased power density. To meet these industry trends, Fairchild Semiconductor (NYSE: FCS) has developed the FDMF68xx Gen III DrMOS multi-chip module (MCM) family.

Designed to enable a reduced inductor and output capacitor count, the FDMF68xx series saves up to 50 percent of board space as compared to conventional discrete solutions and improves efficiency to meet new energy standards. The FDMF68xx series dramatically reduces switch ringing, using Fairchild’s high-performance PowerTrench® MOSFET technology, eliminating the need for using a snubber circuit in most buck converter applications.

The Gen III DrMOS MCM family supports both 3.3V and 5V Tri-State PWM input voltages for both digital and analog PWM controllers and a 30V device option makes the DrMOS adaptable for Notebook or UltraBookTM power systems. Providing better efficiency with over 1MHz switching frequency, increased maximum load current, and greater power density, the Gen III DrMOS series achieves efficiency standards targets while providing up to 60A per phase in a 6×6mm2 PQFN package.

Features and Benefits:

  • 93% at peak and 91% at 30A, 500KHz Frequency. 12VIN, 1VOUT
  • 90% at peak and 88% at 30A, 1MHz Frequency. 12VIN, 1VOUT
  • High current handling: 60A @ 100°C TJ
  • Capable of operating up to 1.5MHz switching frequency
  • Eliminates the need for a heat sink in typical designs

80~120 W Medical Power Supplies

80~120 W Medical Power Supplies

80~120 W Medical Power Supplies

CUI Inc announced a further expansion to their VMS medical open frame power supply portfolio with the release of three new series ranging from 80 W to 120 W. The VMS series is designed to be used in a wide variety of medical and dental applications, carrying UL/cUL and TUV 60601-1 safety certifications and EN55011 class B EMI compliance. All units fit in an industry standard 3” x 5” footprint and achieve efficiencies up to 91%.

The VMS series offers universal input for global operation and is available in wide variety of output voltages ranging from 5 to 48 Vdc. The series can operate from 0° to 50°C at full load, derating linearly to 50% load at 70°C. Features of the VMS series include over-voltage and short circuit protections.

“The VMS-80, 100, and 120 series fill out CUI’s medical power supply offerings from 5 W now all the way through 365 W,” stated Kraig Kawada, CUI’s Director of Product Management. “This broadening of our medical line up will allow CUI to address an increasing number of customer requirements as the medical market continues its expansion,” concluded Kawada. The VMS-100 series is available through Digi-Key with prices starting at $68.14 per unit for 100 pcs. Please contact CUI for OEM pricing.

  • Product name: VMS-80, 100, 120 series
  • Availability: 8 weeks
  • Possible users: Medical and dental equipment manufacturers
  • Primary features: Medical safeties, low no-load power consumption
  • Cost: Starting at $68.14 per unit for 100 pcs

1987 Audi 4000S Main Fuse box Diagram

1987 Audi 4000S Main Fuse box

1987 Audi 4000S Main Fuse box Diagram

1987 Audi 4000S Main Fuse box Map

1987 Audi 4000S Main Fuse box Map

Fuse Panel Layout Diagram Parts: upshift relay, load reduction, horn relay, auto trans relay, intermitten wiper relay, fuel pump, license plate light, interior light, air conditioner, glove compartment light, heater control ilumination.cigar lighter, power seat, control unit, windshield wiper, rear window defogger, turn signal, fog light, emergency flasher, horn, stop light, clock, A/C clutch relay, vanity mirror, socket, cigar lighter, radio, rear window wiper, central locking system, electric mirror, seat heating, side marker light, high beam, indicator light, combination instrument, back up light, luggage compartment light, power supply, fog lamp relay, cooling fan.