Wind Charge Controller Based on the 555 Chip

7/30/2019 Wind Charge Controller Based on the 555 Chip

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A simple charge controller for solar and wind systems

UPDATE This 555 based solar charge controller project has won first place in the UtilityCategory of the 555 Design Contest!!!!! Scroll to the bottom of the page for moreinformation on the contest.

Several years ago I began buildingmy own wind turbines and solarpanels to provide power on myremote, off-grid property. A chargecontroller is an essential part of anywind or solar system to ensure thebatteries aren't over or undercharged. The charge controllermonitors the battery voltage andswitches the batteries off chargewhen they are fully charged, andswitches them back on charge when

they reach a pre-set level ofdischarge. This is a new andimproved charge controller designbased on the 555 chip.

When I originally posted my home-built wind turbine, solar panel and charge controllerdesigns on the web, they became wildly popular. Lots of people all over the world have builttheir own versions. I get flooded with emails every day from people with comments orquestions. A very large percentage of the emails concern problems people are havingbuilding the original charge controller design. While the design is certainly more advancedthan some middle school lesson plans in shop class, it's certainly do-able for any reasonablyskilled person.

The original charge controller design is still working after years of field use. Lots of people allover the world have built copies of it. The original story of the development of this chargecontrollercan be found on my wind turbine page.

Problem is, people with less electronics experience had trouble building it and getting it towork. The circuit was rather complex and confusing for electronics beginners. Some peoplein far-flung parts of the world were having problems finding all the necessary parts. The dailyflood of emails requesting help with building the charge controller have prompted me toredesign it.

So I set myself the goal of greatly simplifying my solar/wind charge controller circuit. I wanted

to get it down to only one IC if possible, and reduce the number of other components asmuch as possible. I also wanted to make sure it only contained easy to find components thatshould be obtainable pretty much anywhere in the world. That way maybe more peoplewould be able to build it without running into problems.

One of my friends suggested I switch to using one of the popular microcontroller chips andreplace all the analog circuitry with one chip. That would certainly get the parts count waydown. However, I was worried that the microcontrollers would be too expensive or difficult toobtain in some parts of the world, and too difficult for non-technical people to program. Idecided to stick with analog circuitry for now, though the microcontroller option is a possibilityfor the future.

w Solar / Wind Charge Controller Based on the 555 Chip http://www.mdpub.com/555C

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Here is the schematic of my originalcharge controller circuit. The heart ofthe charge controller circuit consistsof a voltage divider, two comparators,and an S-R flip flop. My original ideawas to redesign it using the LM339Quad Comparator IC. I'd need two ofthe comparators for this circuit, andcould make an S-R flip-flop using theother two left over comparators onthe chip. I played around with thisidea for a while, and even bread-boarded a few test circuits. I washaving some trouble getting it to workright though. So I shelved the projectfor a while and worked on other

things.

One other project I as working onwas a PWM motor speed controllerfor the pump I use with myrecirculating sluice box that I use forgold prospecting. The speedcontroller uses a 555 timer chip.While looking at a diagram of theinternal structure of the 555 chip, Iwas struck by how closely itresembles my original chargecontroller circuit. Suddenly I realized Icould redesign the charge controllercircuit using the 555 chip and greatly

simplify the circuit and reduce thepart count.

Compare the two diagrams on theleft to see the similarities betweenmy original charge controller circuitand the innards of the NE555 timerchip. The colored boxes representsimilar sections. The 555 timer could

replace 7 components in the originalcircuit, and reduce the totalcomplexity of the circuit a whole lot.This is a very non-traditional and "offlabel" use of the 555 chip, since I'mnot using it as a timer at all. I'mco-opting it's internal organs for acompletely different use than it wasoriginally designed for.


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I set to work. In only a very shorttime, I had a working prototypecircuit bread-boarded. It worked rightthe first try, which is rare for me. I

almost always make some sort ofbone-head mistake wiring things up.

Here is a schematic of the new

charge controller circuit. Click on itfor a larger, clearer version.

I was careful to use only easy to findparts. The NE555 is probably themost popular IC in history. Billions ofthem are made every year. It shouldbe easy to find just about anywherein the world. I also switched to a 5Volt regulator from the 8 Voltregulator the earlier version used.People were complaining they

couldn't find it. The transistor is a2N2222, NTE123, 2N3904, or other similar general purpose small NPN transistor. TheMOSFET is an IRF540 or similar power MOSFET. I just happen to have a bunch of IRF540son hand, left over from other projects. So I used one of them rather than buying somethingelse. Use whatever you can find.

All the resistors are 1/8 watt. 1/4 watt or higher resistors can be substituted if you don't have1/8 Watt resistors. The two trimpots, R1 and R2, should ideally be multi-turn units, butordinary single-turn units can be substituted, with a slight loss of precision in the tuning. Iused 10K trimpots because I already had them on hand. Any value between 10K and 100Kought to work just fine. 10% tolerance is plenty good enough on all the passive components.


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There is no need for any precision parts in this circuit.

The relay is a general purpose SPDT automotive relay rated at40 amps. It should be very easy to find. Get one from an autoparts store, or salvage one from a junked car in a scrap yard. Ihave included a pinout for the relay for ease of connection. 40Amps may seem like overkill, but it allows for expansion in thefuture. You may start with only one small solar panel, then adda few more later, possibly a wind turbine, and a bigger battery

bank. Eventually the charge controller will need to switch some serious current. Why notbuild in the capability from day one? All other parts are specified below.

Most of the parts can be purchased at your local Radio Shack. The rest of the parts can befound at auto parts stores, and online electronics suppliers like Digi-Key, Newark, etc. Youmight find the online suppliers to be much cheaper, especially if you plan on building severalunits and need multiples of each part. You could also try looking for deals on parts onAmazon.com. I buy my automotive relays on Ebay. Even with shipping it is cheaper than theauto parts store, and they are delivered right to my mail box.

IC1 - 7805 5 Volt positive Voltage Regulator R3, R4, R5 - 1K Ohm 1/8 Watt 10%

IC2 - NE555 Timer Chip R6 - 330 Ohm 1/8 Watt 10%PB1, PB2 - NO Momentary Contact PushButtons

R7 - 100 Ohm 1/8 Watt 10%

LED1 - Green LED Q1 - 2N2222 Or Similar NPN Transistor

LED2 - Yellow LEDQ2 - IRF540 Or Similar PowerMOSFET

RLY1 - 40 Amp SPDT Automotive Relay C1 - 0.33uF 35V 10%

D1 - 1N4001 or similar C2 - 0.1uF 35V 10%

R1, R2 - 10K Multi-Turn Trim-Pots

Once I had the prototype working onthe breadboard, I built another unit ona piece of Radio Shack Protoboardfor use in the field. It came togetherin only a couple of hours, and again,worked the first time (I must be livingright lately). This more ruggedversion will get mounted in a box andgiven a thorough testing in the field.

Note that on this board I have chosento use the 78L05 version of the 5 Volt

regulator. It is in a tiny TO-92package, the same size as the2N2222 transistor. It is the small,black rectangle on the upper left

corner of the board. It saves a lot of board space. It can only handle 100 mA, but that isplenty enough to power this circuit. If you can't find the little 78L05, you can use the full sizeTO-220 version of the 7805, which is much more common. There will be no penalty otherthan using up a little more board real estate. I just happened to have a few of the 78L05s leftover from another project.

Once you have the circuit built, it is time to tune or calibrate it. I use 11.9V and 14.9V as my

Click on alady

to learn how

to meet her.


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low and high set points for the controller. These are the points where it switches from sendingpower to the batteries to dumping power into a dummy load, and vice versa (a dummy load isonly needed if you are using a wind turbine, if using only solar panels, the dummy load linecan be left open).

Probably the best way to tune the circuit is to attach a variable DC power supply to thebattery terminals. Set the power supply to 11.9V. Measure the voltage at Test Point 1. AdjustR1 until the voltage at the test point is as close to 1.667V as you can get it. Now set yourvariable power supply to 14.9V and measure the voltage at Test Point 2. Adjust R2 until thevoltage at the test point is as close to 3.333V as you can get it.

Test the operation of the charge controller by running the input voltage up and down betweenabout 11.7 and 15.1 Volts. You should hear the relay pull in at about 14.9 Volts and open atabout 11.9 Volts. In between the two set points the controller should stay in whichever state itis in. The Charge and Dump buttons can be used to change the state of the controller whenthe input Voltage is between the two set points.

Before you write to me and tell me that my lower set point is too low and I amover-discharging my batteries, consider that the battery voltage isn't normally going to getthat low except under load. If the load were removed, the voltage would recover over timeback up to well over 12V. So the batteries aren't as deeply discharged as you might think at

first glance.

Once I had the circuit working, Imounted it inside asemi-weatherproof enclosure. Therelay is on the left side. I used abarrier strip to make wiringeverything together easier. I usedheavy gage wire for all thehigh-current connections. This thingwas designed to switch up to 40Amps after all. I also included a fuse

in line with the solar/wind input line.

Click on the image for a larger view.

Here is another view with the lid inplace. I used this enclosure becauseI happened to already have it onhand, not because it is the best onefor the job. For permanent outdoor

use I would prefer to use a morerugged and weather-proof enclosurelike I did formy original chargecontroller design. However, I like thefact that I can see the LEDs throughthe translucent lid and tell whichstate the charge controller is in at aglance, and I didn't have to drill anyextra holes in the box for the LEDs.This box will work for field testingpurposes.


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Click on the image for a larger view.

Here is a side view of the unitshowing the feed-through barrierstrip with all the connections to theoutside. There are connections forthe positive side of the battery(s), thepositive input from a solar panel orwind turbine, the positive side of anoptional dummy load, and threeground connections.

When hooking up the chargecontroller, the battery should beconnected first. That way theelectronics will have a stable sourceof power. If a solar panel or windturbine is connected first, the

controller is liable to wildly oscillate between states.

I should explain about dummy loads. The type of wind turbines I build have no real provisionfor braking or furling in high winds. It is only the presence of a constant load on them thatprevents them from over-reving in high winds. So when the charge controller senses that thebatteries are fully charged and switches them out of the circuit, it switches in a dummy load(just a big external bank of high-wattage resistors) to soak up the power output of the windturbine and keep it under load. If you are using a commercially made wind turbine withbuilt-in over-rev protection, or using only solar panels, then the dummy load isn't necessaryand you can leave the dummy line unconnected. You can learn more about dummy loads onmy wind turbine page.

Here is another side view showing

the charge and dump buttons. Thecharge controller will automaticallyswitch between charge and dumpwhen the battery voltage reaches thelow and high set points. Between theset points the controller will remain inwhichever state it is in. These buttonsallow me to manually toggle thecharge controller between the twostates.

Here is a photo of the first real fieldtest of the new charge controllerdesign. It seemed to be workinggood in my bench tests, but I wantedto make sure it worked right underreal-world conditions. So I set up oneofmy home-made 60 Watt solarpanels outside my workshop and


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used it to charge up a deep-cyclebattery using the new chargecontroller. It worked great. Thecharge controller let power run intothe battery until it was fully chargedand then switched to dumping powerso as not to over-charge the battery.

Perfect!

Click on the photo for a larger version.

Here is a closer photo of the setup.The battery is a 36 AH deep-cycleunit often used in personal mobilityscooters and motorized wheelchairs. I find that they work well insmall-scale wind and solar powersystems. The Volt meter is showing12.64 volts on the battery, which isessentially fully charged. The battery

was nearly fully charged when Istarted this test. It took only a shorttime for the solar panel to top it offand the charge controller to switchover to dumping. A highly successfultest.

The only issue I had during the test was seeing which of the LEDs was on in the brightsunlight. In normal use though the charge controller would be mounted in a sheltered andshady spot out of the direct sunlight.

Click on the photo for a larger version.

Here is a brief video I shotduring the test run. It showshow the charge controllerautomatically switches overfrom charging to dumping whenthe upper set point is reached.

Multiple solar panels and/or windturbines can be connected to thisunit. All the power sources can be


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connected in parallel and fed into thesingle input connection. Eachindividual solar panel or wind turbineneeds to have its own blocking diodethough. Here is a diagram of atypical system with a wind turbineand two solar panels feeding thecharge controller. Typically an AC

inverter is included in the system topower AC loads. Click on the imagefor a larger version.

People write me and ask why they need a charge controller and batteries? Why not justconnect the solar panel or wind turbine directly to the inverter and be done with it? Well, theanswer is that the sun doesn't always shine and the wind doesn't always blow, but peoplewant power anytime. The batteries store power when it is available, for use when it isneeded.

I may develop a printed circuit board for this project, if time permits and there is sufficientinterest. I'll post further updates on this project as it progresses.

UPDATE

My friend Jason Markham hascreated a PC Board layout for thisproject almost as soon as I posted it.

Click the PCB to go to his web site.

UPDATE

People are writing me and asking if this charge controller can be used with 24 Volt systems,and what changes would be necessary. The circuit should work fine for 24 Volt systems. Therelay will need to be replaced with one rated for 24V coil voltage, and the pots will have to bere-calibrated for new high and low set points for the higher battery voltage. The 7805 voltageregulator is rated for up to 35 Volts input voltage, so no other changes in the circuit should benecessary.

UPDATEIn an effort to create a compact, neatand portable solar power system, Ihave mounted the charge controlleron top of a battery box. I have alsomounted an AC inverter on the box.This is a much larger and highercapacity battery than I was using inmy early tests of the chargecontroller. The inverter and chargecontroller are mounted on the battery


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box with industrial strength,sticky-back Velcro.

Here is another view of the setup. Asyou can see, I have also included acigarette lighter style plug forpowering 12V DC loads. It is acomplete solar power system in one

small (but heavy) package. All I haveto do is connect a solar panel or twoto it. I can't wait to try it out on mynext camping trip. I'll have plenty ofpower in the wilderness.

I have finally decided to ditch my oldbattery bank, which I had been

lugging around on my wildernessoutings for years. It was a bank of 14smaller 12V AGM batteries. I got thebatteries essentially for free, so Iwired them in parallel, put them in aplastic bin, and used them with myportable solar/wind power system.The setup was very heavy andunwieldy. I kept telling myself I'd getrid of it and go with one big batteryonce the little batteries started dying.They hung on for years and years. I

must have been treating them right.Finally they started loosing capacity and dying off one by one. So I went out and bought onebig battery to replace them all. It is about the same size and weight as a car battery, but it is adeep-cycle design, perfect for solar/wind systems. It has about the same AH capacity as theold bank of 14, but is much smaller and quite a bit lighter. It only set me back about $200. If itlasts as many years as the old bank, I'll be very happy. My back will also be happy that I don'thave to lift the old bank of 14 batteries anymore.


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UPDATE

This 555based solarchargecontrollerproject haswon firstplace in the

UtilityCategory ofthe 555DesignContest!!!!!Yahooooo!

For anyoneinterested,here is aYoutubevideo of

ChrisGammelland JeriEllsworthannouncingthe 555contestwinners.The bitwhere theytalk thisproject at

about the47 minutemark.

Just to clear up one detail mentioned in the video, this project was not actually created to bea contest entry. I had already had my "Eureka Moment" about using the 555 to replace awhole bunch of parts in the original design, and was building the prototype before I evenheard about the 555 Contest. It just turned out to be great accidental timing. Hearing aboutthe contest did spur me to quickly finish the prototype and get this web page up in a timelymanner though.

Many thanks to Jeri, Chris, the other judges, and the sponsors of the contest.

Our fantastic deals ofhollister uk and Pass4sure 640-802 make your success certain for thefinal Testking 642-902 exam.You can get Testking 350-001 and Testking VCP-510 easily fromour website.

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Wind Charge Controller Based on the 555 Chip