Series Diode Voltage Regulator

Want to power this with solar panels?

I want to build a standalone wifi repeater -- powered by the sun. The problem is how much solar power and how big of a battery?

net draw 4.5v @ 0.66A with load
net draw 4.5v @ 0.60A no load

I'm assuming the best choice would be a 6v battery with a a couple diodes in series to induce ~1.5v drop. Then, I need something to charge it -- I found 12v 6w solar chargers in the automotive section of Sears and 16v 2w solar chargers in the marine section of Dick's Sporting Goods.

How many solar panels and what capacity batteries should I use? Is this the best method or should I use a voltage regulator and go with 12v batteries?

I need this to be as cheap and simple as possible...
I never said anything about using an inverter, changing DC into AC back to DC is just stupid...I'm saying to use a REGULATOR which takes a range of higher voltage, unregulated DC and outputs lower voltage, regulated DC. This is how most car-cellphone chagers work (cellphones use 4-6v to chage)

You will find a much larger selection of system components to make a 12V solar system rather than a 6V solar system. So you might consider finding a switching regulator to drop 12VDC down to 5VDC, then use a diode to further drop it to about 4.4V. A switching regulator can be had with efficiencies in the 85% range. Avoid a linear regulator; its efficiency will be less than 5/12 = 42%.

Assume the following design criteria (adjust to your liking):
1. battery to be a deep-cycle (a.k.a marine battery)
2. battery discharging stops at 20% capacity
3. battery nominal voltage 12Vdc
4. run-time on battery 3 days between charging (due to cloudy days)
5. effective charge time 6hours/day at full output (this depends on your lattitude and season).
6. 12Vdc/5Vdc switching power supply with 85% efficiency
7. Load is a continuous 0.66A at 4.5V
8. Battery charging is 78% efficient
9. Solar panel operates at 17.1V output (maximum power point)

Calculations:
The needed battery capacity (to 20% charge) in ampere-hours is:
0.66A x 24h/day x 3 day x 5V/12V / .85 / .80 = 29.1AH

The number of kWh needed per charge cycle (6 hours) is:
29.1AH x 17.1V / .78 = 638 VAh ==> 0.638kWh

The average current required during the 6-hour charge cycle is:
29.1AH / 6H / .78 = 6.22A

The nominal solar panel size required is:
6.22A x 17.1V = 106W

Most solar panels today are constructed of strings of 36 individual cells. These panels require that a solar charger be used to regulate the charge current (to preclude overcharging the battery). A simpler system is to obtain a solar panel with 33 cells per string. This is considered to be a self-regulating panel that can be connected via a diode to the battery, without a charge controller. It is a less expensive system, but it won't charge as well as a 36 cell panel will on an overcast day.

As cheap and simple as possible...
Consider relaxing your design criteria. E.g., allow outages after 1 day. Power down the access point at night or during periods that it isn't used.

Good luck! Sounds fun.

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Furman P-2400 AR Voltage Regulator/Power Conditioner $1799.95 The Furman 20 amp P-2400 AR power conditioner and voltage regulator delivers a stable 120 volts of AC power to protect audio equipment from problems caused by AC line voltage irregularities such as sags, brownouts, or overvoltagesall of which can cause sensitive electronic equipment to malfunction or sustain damage. The Furman P-2400 AR regulator/power conditioner accepts input voltage between 97V-137V and transforms it to a constant output of 120V, ±5V. Voltages beyond that range may also be converted to usable levels, depending on the range variance. With it's robust 20A capacity, the Furman power conditioner and voltage regulator is ideal for high-current equipment such as power amplifiers or powering A/V racks in large installations.Additionally, the Furman P-2400 AR is a full-featured power conditioner that filters and purifies AC power, reducing line noise and ensuring optimum performance. Not only will your equipment perform better with Furman's Linear Filtering Technology (LiFT), but it will also be fully protected by their exclusive Series Multi-Stage Protection (SMP) and Extreme Voltage Shutdown (EVS) features. This circuitry provides an extremely high level of power protection.True RMS Voltage Regulation delivers stable voltage output (selectable between 230V and 240V) to protect equipment from problems caused by AC lne voltage irregularitiesFurman's exclusive SMP technology provides the highest level of surge & spike protection availableLiFT offers AC power filtering to ensure clean power for unequaled audio & video clarityAdvanced EVS circuitry detects dangerous voltage irregularities and safely powers down itself and connected equipment in unsafe conditionsLED status indicators warn you when voltage is outside of nominal range or when protection has been compromisedLarge LED voltmeter/ammeter displays incoming voltage and output current drawIsolated outlet banks minimize inter-component interference and noise contaminationFront panel USB convenience outlets allows you to charge most media devices or power a USB lamp20 amp rating featuring a high inrush magnetic circuit breaker for added protection14 total outlets (twelve rear panel outlets and two front panel convenience outlet)

Furman P-2400 Ar Voltage Regulator/Power Conditioner $1799.95 The Furman 20 amp P-2400 AR power conditioner and voltage regulator delivers a stable 120 volts of AC power to protect audio equipment from problems caused by AC line voltage irregularities such as sags, brownouts, or overvoltagesall of which can cause sensitive electronic equipment to malfunction or sustain damage. The Furman P-2400 AR regulator/power conditioner accepts input voltage between 97V-137V and transforms it to a constant output of 120V, 5V. Voltages beyond that range may also be converted to usable levels, depending on the range variance. With it's robust 20A capacity, the Furman power conditioner and voltage regulator is ideal for high-current equipment such as power amplifiers or powering A/V racks in large installations.Additionally, the Furman P-2400 AR is a full-featured power conditioner that filters and purifies AC power, reducing line noise and ensuring optimum performance. Not only will your equipment perform better with Furman's Linear Filtering Technology (LiFT), but it will also be fully protected by their exclusive Series Multi-Stage Protection (SMP) and Extreme Voltage Shutdown (EVS) features. This circuitry provides an extremely high level of power protection.True RMS Voltage Regulation delivers stable voltage output (selectable between 230V and 240V) to protect equipment from problems caused by AC lne voltage irregularitiesFurman's exclusive SMP technology provides the highest level of surge & spike protection availableLiFT offers AC power filtering to ensure clean power for unequaled audio & video clarityAdvanced EVS circuitry detects dangerous voltage irregularities and safely powers down itself and connected equipment in unsafe conditionsLED status indicators warn you when voltage is outside of nominal range or when protection has been compromisedLarge LED voltmeter/ammeter displays incoming voltage and output current drawIsolated outlet banks minimize inter-component interference and noise contaminationFront panel USB convenience outlets allows you to charge most media devices or power a USB lamp20 amp rating featuring a high inrush magnetic circuit breaker for added protection14 total outlets (twelve rear panel outlets and two front panel convenience outlet)

Furman P1800AR Advanced Voltage Regulator and Power Conditioner $899.95 The 15 amp Furman P1800AR Advanced Voltage Regulator and Power Conditioner delivers a stable 120 volts of AC power to protect equipment from problems caused by AC line voltage irregularities such as sags, brownouts, or overvoltages, all of which can cause sensitive electronic equipment to malfunction or sustain damage. The Furman P1800AR accepts input voltages over a wide AC voltage range and transforms it to a constant output of 120V, ±5V. Voltages beyond that range may also be converted to usable levels, depending on the range variance. Additionally, the Furman P1800AR is a full-featured power conditioner that filters and purifies AC power, reducing line noise and ensuring optimum performance. Not only will your equipment perform better with Furman’s Linear Filtering Technology (LiFT), but it will also be fully protected by our exclusive Series Multi-Stage Protection (SMP), and Extreme Voltage Shutdown (EVS). This circuitry provides the highest level of power protection available. Furman P1800AR Voltage Regulator and Power Conditioner Features: SMP Surge Protection: Furman's exclusive SMP technology provides the highest level of surge and spike protection available LiFT Noise Filtration: LiFT offers AC power filtering to ensure clean powr for unequaled audio and video clarity EVS Voltage Protection: Advanced EVS circuitry detects dangerous voltage irregularities and safely powers down itself and connected equipment in unsafe conditions Diagnostic Lights: LED status indicators warn you when voltage is outside of nominal range or when protections has been compromised True RMS Voltage Regulation: True RMS Voltage Regulation delivers a stable 120 volts of AC power to protect equipment from problems caused by AC line voltage irregularities USB Charger: Front panel USB convenience outlets allows you to charge most media devices or power a USB lamp Isolated Banks: Isolated outlet banks minimize inter-component interference and noise contamination Voltmeter / Ammeter: Large digital voltmeter/ammeter with discrete dimmer button displays line voltage and true RMS current draw Wall Wart Spacing: Three widely spaced outlets accommodate bulky AC power transformers 15 AMP Rating: 15 Amp rating featuring a high inrush magnetic circuit breaker for added protection Nine Total Outlets: Nine total outlets (8 rear panel outlets and one front panel convenience outlet) BNC Lamp Connector: Rear Panel BNC connector powers any standard gooseneck lamp for rear rack illumination

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Voltage Regulator - How it Works Part 1

Zener diode circuit, electronics help?

Draw a schematic diagram of a Zener regulator with: Supply voltage of 20Volts, a zener voltage of 12Vlts, a series resistance of 330(ohms), and load resistance of 1k(ohms).

What is the Zener current and load voltage?

Help is much appreciated.

here are some schematics

http://images.google.ca/images?hl=en&um=1&sa=1&q=12V+zener+circuit&btnG=Search+images&aq=f&oq=&start=0

your circuit will deliver 24 mA max
The top right circuit is much more powerful. (if 12V zener is not available)

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