Hand Crank Generator.

[marshalldtk]

I've been looking on line for plans to build a small hand crank generator, one that will power a 9v transistor radio. Ive seen them for sale but more interested in making one myself. The ones that ive seen say that you crank for 30 sec and get 15 min of play time. Any help on plans? (im very much a novice at electronics so excuse me if this seems simple)

[jollyrgr]

This is not too hard for a novice nor do I find it silly. In fact I have a squeeze flashlight, three crank flash lights and a crank radio right now. One of the flashlights is something I "sort of" built. But let me give you some background first.<p>I have found these types of things very intersting ever since I was a young kid (kindergarden or first grade). The first one of these hand crank things I had was a toy flashlight. It was called a "FLASH BRIGHT". It was a small dynamo built into a "flashlight like" case. The thing came with a clear lens and RED, YELLOW, and GREEN filters. The crank was removable and everything stored in a holster that you wore on your belt. Only down side is as soon as you stopped cranking the light went out. And it took two hands to keep the thing lit. I remember telling my mom that I wished you could crank the thing for a few seconds then keep it lit. It eventually wore out but I still wish I had it. (I have searched for these on the Internet and even on eBay. I have yet to find one out there. If anyone knows of a link or web site that talks about this toy, please send it to me.)<p>I some years later I saw something ALMOST as good but they were always expensive. These were "batteryless" squeeze flashlights. These had a handle on the side that you would sqeeze that would then turn a flywheel and eventually a generator. Think of it like one of those hand exerciser springs. This was a slightly better step than the two handed crank toy. Still you got a workout with them. For some reason I always recall these as being "Russian made". I have one of these right next to my bed but mine is not Russian. Mine is a relic of the 1970's energy crunch. Here is an example of this type of light; complete with a picture of the insides. There is also a short movie of the device in operation.<p>http://www.modernoutpost.com/gear/detai ... flash.html<p>For a number of years I have been wanting to build something even better. Then I heard of the Baylis Clockwork radio and realized somebody had beaten me to the punch. The Baylis Clockwork radio is now known as the Baygen Freeplay radio. There is a long line of devices built on this principle. The Baygen system uses a mechanical rather than chemical or electrostatic method of storing energy. With the Baygen radios you turn a crank. This crank then winds a unique flat spring from one spool to another. As the spring unwinds it turns a transmission set of gears. This set of gears then spins a standard electric motor (like those commonly found in tape, CD, or DVD players) to generate electricity. This energy is then fed to a standard radio circuit. Anytime I have posted information about the innards of a Freeplay I get requests for the type of motor that is being used as a generator. In reality you can use almost any type of DC motor. But to satisfy everyone, here is the spec. sheet from the Radio Shack version of the Freeplay radio:<p>http://support.radioshack.com/support_a ... /50742.htm<p>For those that don't want to search the link, the motor is a Mabuchi RF-500TB. This motor, acting as a generator, puts out 3 volts at 35mA when spun at 1500 RPM. For those that want more information, here is the link to the specific motor:
http://www.mabuchi-motor.co.jp/cgi-bin/ ... D=rf_500tb<p>Freeplay has come up with another intersting gadget. This is the FREECHARGE by Motorola and Freeplay radio. This is a neat device that is used to charge cell phones. 45 seconds of cranking gives about five minutes of talk time. Unfortunately it is next to impossible to find it in stores. So far only ONE cell phone store I have been to even know of its existence. The order price for new is quite expensive; about $50 to $85. This version of the device uses a set of gears to turn a STEPPER motor of some sort. The stepper motor then charges either NiCad or NiMH batteries inside the Freecharge unit. The neat thing about this setup is that you can charge the batteries using the wall charger or car charger. If the batteries die you can recharge them with the hand crank. If your phone is plugged into the Freecharge, turning the crank will charge both the internal Freecharge batteries and the cell phones batteries. I have two of these units and can only say, except for the internal batteries, these things are built to last. I do not use them for charging phones but for the "flashlight" module that comes with them. Mine came off of eBay for less than six bucks each. There are a number on eBay right now for under $15 for the BUY IT NOW type auction. The Baygen company makes a number of radios, flashlights, the Motorola co-op charger, and items for the Coleman "outdoor" company. Their main goal is not for Western world but for third world countries. They provide distant learning radios to people in the remote areas of Africa. I read stories that I cannot confirm about Freeplay making radios for the US government that were dropped into remote locations of Afganistan by the US military. I do not know how true this really is. I saw a TV special on the Baygen company a few years ago. They were supposed to come up with a "universal" charger that could be used to recharge laptops, power your own radio, or just about anything electronic. I have not seen this device yet. But the Freecharge cell phone gadget they make comes pretty close. Anyone with minor electronic skills could modify this item and use it to power a number of battery operated items.<p>Since Motorola and Freeplay came up with their device for charging cell phones, there have been a number of knock-offs. All of these I have seen are from Pacific Rim countries. These are much more simpler as they do not have internal batteries to worry with and only recharge the cell phones batteries and possibly a small internal capacitor. Here is one such example called the SideWinder:<p>http://www.sidewindercharger.com/<p>I have a similar version to this one BEFORE the capacitor and LED was added. Back when the knock-offs came out (specifically the SideWinder) I exchanged e-mails with a vendor of these items. An eBay ad made it sound as if this item had a built-in LED flashlight. I asked specifically if it did. The response was no, the LED is only for indicating that the crank is being turned fast enough to charge batteries. A few days later the person wrote back and asked if I would be interested in the SideWinder with a flashlight. I wonder.... In any case eventually purchased a different style of one of the knock-offs. Again it was from eBay. You can buy the knock-offs for about $5.00 to $10.00. I used some 1 Farad "memory" capacitors and 10,000 mcd white LEDs to make a flashlight module. I can get about five minutes of light time for 30 seconds of crank time. Both the Freecharge and the hand crank knock-off put out about six volts. Search eBay for "HAND CRANK CELL PHONE" If you are lucky, cell phone stores near you might be selling these items. I live near the Chicago suburbs and could not find these except at one ham fest. You might have better luck.<p>Now, to answer your question. You can buy one of the above or you can make your own. There was an article in a back issue of Nuts & Volts that covered making a flashlight that cranked. But the project presented was rather lacking. I will give you a small overview of what you will need to do:<p>
1. Decide how you wish to store energy.
You stated you wanted to crank for 30 seconds and get 15 minutes of play time. Thus you must put in enough energy from your muscles and store it in some form. There are three main ways to do this. Mechanically (using a spring or rubberband), electrochemically (rechargable batteries), or electrostatically (capacitor bank). The Freeplay radios use a specialized spring to store mechanical energy. This spring is VERY DANGEROUS. I strongly recommend NOT using any sort of spring on your own. The Freecharge uses standard rechargable batteries. I have not examined either of my devices batteries to determine what exactly their makeup is. They appear to be either NiCads or NiMH. If I were to make one, I would use the NiCads as they are usually cheaper and less "fussy". For my flashligh item I skipped batteries altogether and went with memory capacitors. One charged capacitor lights up one 10,000mcd white LED for about five minutes with more than enough light to read by. Rubber bands WILL FAIL. I cannot believe how many times I see people using rubber band power on shows like Junkyard Wars. A rubber band will hold papers together, hold a pony tail, secure a small box, or MAYBE power a small airplane. It should not be used to store energy for a project like this.<p>2. Layout your mechanical setup and gear train.
This WILL be the hardest part. Unless you know of or can construct some sort of hand crank module that will spin a small motor you will have a difficult time with this project. The mechanical part (for me at least) was the biggest hold back. Even when I made my device I elected to buy a ready made crank unit. The item I have is a series of gears, a small motor like those found in a tape or CD player. Circuitry is nothing more than four diodes, a capacitor, and an LED and resistor in series. The "external" circuitry for my circuit is a 1F capacitor, a SPDT switch, and a white LED. The switch is arranged so that in one position the positive of the cap is connected to the hand crank dynamo device. This is the LED off and "charge" position. The other position connects the LED to the capacitor. Grounds are all common connection.<p>3. Charge circuitry and the radio.
For me this is extremely simple. The Freeplay radio I have will fill a room with sound and receive a great signal powered by only three volts. Using a lower voltage means fewer batteries in series. Or, if you go with a bank of memory capacitors, you can get by using the 1 FARAD units. (They do not like voltages over 5 volts for the type I use.) If you want someone to describe how to build a radio from scratch, forget it. This would be well beyond the scope of such a project. There are plenty of radios that will run on two AA, C, or D batteries (read 3 volt circuits) and give plenty of volume. Radio Shack has several models for sale now. But you can use higher voltages (9 volts) if you desire. <p>To make things simple (you stated you are a novice) use a TWO WIRE motor and avoid stepper motors. Take the two wires from the motor and connect them to the AC input of a bridge rectifier circuit. You can use four power diodes or a bridge circuit in one package. Since you are a novice, start with a bridge in one package. It will save you grief in figuring out a bridge circuit and possible problems. If you go with a rechargable battery solution throw a 100uF electrolytic capacitor on the output (DC side) of the bridge rectifier circuit. Your charging circuit should be easily isolated from your radio (i.e. a switch to turn off current from flowing from the charge circuit to the radio). Once you do your cranking, turn the switch back to the radio device.<p>[ May 26, 2004: Message edited by: Jolly Roger ]</p>

[Chris Smith]

Nuts and volts had a good article on the subject a few months back. A good source for the generator is the Old 5 1/4 floppy disk motors, full height. They produce lots of current especially if you gear up the crank input. Diodes on all the leads out, and super caps as the storage mechanism, with white LEDs as the bulb. Regulation if necessary, either the buck boost or the conventional methods.

[perfectbite]

Regarding your gear train. I am assuming that you have a garage work bench (hopefully with a vise). If you have easy access to a Tap Plastics store or similar there may be scrap 1/8" and up sheet pieces of ABS or a 'pumped' (bulked up with tiny air bubbles) PVC called Komatex. ABS and Komatex are excellent for working with. They are strong and tough, (the ABS is tougher than the PVC) they cut easily and drill and tap easily and, best of all, they superglue easily. (the Komatex doesn't like sunlight though). It should be quite easy to drill fastening holes for the generator motor and its shaft. AllElectronics (Van Nuys, CA) has a grab bag of black plastic gears that don't glue well but don't go to the local Bearing Engineering place for metal or phenolic or nylon filled gears, they will charge you an arm and a leg. Because you would want to put a lot of stress on the gear train and its case I would go with at least 1/4" ABS that way there will be enough 'meat' on the holes to support the gear shaft's sideways push. Careful laying out of the gear teeth's engagement and hole placement can be done by using a pair of dividers and one's eyeballs. Very carefully enlarge the cheapie gear's centre holes keeping them centered. Hobby stores carry smallish PVC sections and, if you can find it, use a hardish plastic rod, polished fibreglass would be excellent (styrene is too soft for extended use) and slightly roughen the surface of the rod and use the plastic epoxy to bond the gear plastic to its shaft. Don't make the crank handle so big that the torque from the turning stresses and shears the cranking gear shaft. (Perhaps someone else could come up with a way not to have to epoxy the cranking wheel to this small shaft?) Using one of the larger gears, drill a hole toward the outer rim of it and use a size 10 pan head machine screw, nutted on both sides (allow clearance, use washers and lockwashers), at the gear with a piece of copper or plastic tube held in place by a nut at one end and the screw's head at the other that will spin as the crank is turned to save ripping your fingers up. Epoxy this assembly to the shaft. Use milk bottle plastic to cut shim washers out with scissors as needed. Stack and glue (using plumber's plastic epoxy) the gears together (teeth lined up) if you have to to prevent the relatively soft plastic teeth from deforming under the load. Use stacked circuit board spacers to seperate the gear box plates. Connect your circuit and crank her up. Don't forget, the motor will keep on turning the crank as it winds down. This is the economy version.

[marshalldtk]

Thanks for all the info. Now I just have to take your directions to radio shack and have them to set me up with the capacitors (hopefully they'll know what it is!) gives me a good project to work on until camping season starts. (i live in Montana and we had 4 inches of snow just last week) thanks again you all have been tons of help.

[jollyrgr]

You will not find the 1 Farad capacitors at Radio Shack. They carried them one time years ago but not any more. Do not get the car stereo one farad capacitors! If your Radio Shack sales person does not know any better they might direct you to that type of capacitor. The ones you want are about the same size as three to five pennies stacked on top of one another. Here is one source:<p>http://www.allelectronics.com/cgi-bin/c ... -12&type=s tore

[perfectbite]

Jolly Roger. This is off the subject but why do you not recommend the 1 Farad car audio caps from RS? I've been given to understand that generally a cap is a cap is a cap.<p>Also the reel to reel flat springs you mention are called Tensor springs and are used as balancing springs for operator positioning of 'relatively heavy' equipment like X-ray platens &c. Quite nifty devices actually.<p>Also, in thinking of it. Your way to crank one of these is probably the better way to go. Little muss, more rugged, minimum cost and it looks a lot better than a home-made effort. However, starting from scratch at home, if one tells someone, "I made it." the reply usually is "I can see that."

[haklesup]

"I've been given to understand that generally a cap is a cap is a cap."<p>Only on paper. The "memory caps" recommended only have a voltage rating of about 5V or less. Put that in your car at 12V and you get smoke. The big caps used for cars are very expensive. I'm sure he dosen't want a $100 generator.<p>A NiMh battery is generally cheaper than both types of caps and will hold far more charge than either one (however, since the capacity is larger, from a dead start, you will spend more time cranking to get to the minimum level needed to power a radio but it will run longer)<p>Does anyone know how to compare Farads to mAh. In other words, How long would a 1F cap supply 1mA to a load.<p>Best to start with a radio that runs at low power to begin with, this will extend the time it will run between cranking. Loud volume will use power very fast, an earphone will save lots of power.<p>Back to caps: Each type of cap has different tolerance, voltage range, leakage, ESR, thermal properties etc. For example, ceramic caps have good frequency response, can be gotten for almost any voltage and have low leakage and low cost which makes them good for decoupling DC supplies near IC chips but since the tolerance can exceed 80% they would make a poor choice as a critical timing component.

[jollyrgr]

Thanks haklesup, you got most of what I would have said. <p>Not all Radio Shacks are owned by Tandy. Some stores say "Radio Shack" on the outside but are only "partly" Radio Shacks. They may sell other things from other companies as well. Some of the Radio Shack workers might know of the expensive mega car stereo 1 Farad capacitors. In my area car stereo stores as well as places like Circuit City and Best Buy sell the 1 Farad "stereo" capacitors. Many RS employees will not know of the 2.5V and 5.5V memory capacitors. If Radio Shack is carrying these again I have not ever been able to find them. <p>Thanks for the name of these springs. I still say these things are dangerous. I know the problems that can be caused by a small one like those found inside a tape measure. My "older" Freeplay radio has warnings on the outside of teh case not to open it up. I did anyway. Inside there are even more warnings on the gearing/transmission/spring ass'y warning me not to open it. This is no Slinky spring. And based on the winding effort I do not want to take a chance opening this thing. And for someone to try and build something from scratch using one of these does not seem like a good idea. Blowing up a capacitor or seeing the spark it makes when you short out a five volt one farad capacitor is nothing compared to the hundreds of pound of force behind that spring. <p>The winding effort on my little contraption is quite high at first. I've gone as high as three 1 Farad capacitors in parallel using my little generator. It is quite difficult to start to turn this thing. <p>I have also played with motors much larger than the little CD player motors I spoke of. One such motor was from either a laser printer or large ink jet printer. It was a standard DC (not stepper) motor that ran on (according to the label) 19V. Shorting the lead out and turning by hand was next to impossible. I tried hooking single Christmas lightbulbs to the leads and spinning the motor. Even with two fingers I could spin it fast enough to burn out the lights. Thus maybe a larger motor and only two gears would work much better.

[sofaspud]

>Does anyone know how to compare Farads to mAh. In other words, How long would a 1F cap supply 1mA to a load.<p>This seems fairly easy - I'll probably get it wrong! But anyway, the answer is found from the RC time constant (t). At 5 volts, a resistive load of 5k ohms will draw 1mA. t=RC which would be 5000 seconds, or about 80 minutes.