Newbies with circuits, want to make a solar powered night light for my room. (inc. photoresistor)
199397
I agree that a relay is useless.  Everything needs to be very low power (i.e. use MOSFETs).  Capacitors might work if you use the new "ultracapacitors", or DLC's, which have huge capacitance and tiny leakage.\n   Since it's solar powered, you'll have a photocell.  You can use this also as the light detector.  When the photocell is producing current, charge your battery or ultracapacitor.  When photocell voltage drops below some threshold, turn on the LED.\n   A simple way to go would be to use two or three photocells in series, and run through a diode to your battery/ultracapacitor.  THen, run the battery/capacitor positive terminal to the source of a p-channel MOSFET, and run the drain to your LED (with a series resistor to control brightness).  Control the gate of the MOSFET with the positive terminal of the photocells.\n   When the photocell voltage drops a few volts below the battery, the MOSFET will turn on, energizing the LED.  When the photocell is .7V more than the battery voltage, the battery will charge.
234029
Use a darlington array. They make them with 6 or more darlington transistors on a single chip. Some even have the circuit protection diodes built in. These are perfect for stepper motor control circuits. If you don't want to buy them, you can probably scavenge a couple from a dead printer or copier, if you can get one.\n\nOther than that, there is no best transistor. This is a general, low speed switching application, and almost any transistor that can handle 160mA at your circuit's voltage can be made to work with the proper biasing. But a single chip to replace several transistors and diodes will simplify your PCB.
265915
a light needs 60W , and a fan need 60 W. so if u have 10 lights and 5 fans u need 15 x 60=900W\na solar cell (1m x 2m) contains 90~100W so \nfor 10 lights and 5 fans u need 10 (1m x 2m) solar cell..\nif the numbers of lights and fans different u can use the solution above..
666927
here is a link which I hope will help. http://www.hgtv.com/hgtv/dc_lighting_other/article/0,1793,HGTV_3466_1372885,00.html \n\nyou may have to adapt the info to the flower pots you want to use.  it has clear pictures to illustrate the process.   have fun!
37539
This might help\n\nhttp://www.ttec.co.tt/consumertips/conserveelectricity/default.htm
157030
Go to microchip.com for chip specifications. Have 6 outputs to LEDs. green/yellow/red for each direction. Make timing loops in basic. MIKE
502438
Take a look at this site;\n\nhttp://www.solarfuse.co.uk/\n\nThis is a friends, he is always looking for new flash designers.
74298
Here are some sites that may help.  Both have circuit examples utilizing LVDT's.  Hope this helps.
343735
Ok, at the risk of being blunt, if you need to ask this, you might be better of leaving things well alone - or doing as the other person suggested and using a transormer to lower the voltage to begin with.\n\nHowever.........\n\nFirst of all, you need to plonk a diode in line really, LED's do not like AC so the diode will make things into "raggy DC", using a bridge rectifier would be better and would reduce the flickering, as would plonking a capacitor over the DC output - typically with AT LEAST a 380V rating if using a bridge and a 200V rating if using a single diode.\n\nStill with me?\n\nYou now need to work out the voltage drop over the LED's - this varies according to type - and mainly colour. About 1.8V for a typical RED LED and around 4v for a white one.\n\nYou then need to look at how many volts you have "left" after you have taken into account all of the LED's in series.\n\nEG:  You take 220V, use a single diode (110 v) and then pop a cap over to stop the flicker (around 160V)\n\nYou now have 30 red, 20 green and 10 blue LED's in series. Assume 1.8V drop on Red, 2.2V on Green and 4.1V on blue.\n54v  + 44v + 22v = 120v\nThis gives us 40v to "burn off" with a resistor.\n\nLet us assume you want to drive the LED's at 20mA\n\nR = V/I   therefore  R = 40/.02 = 2000 Ohms\n\nPower = I x I x R  (current sqaured 8 resistance) so the resistor will be dissipating 800mW - Allowing for plenty of play and wanting a warm rather than hot resistor, then 2w ideally.\n\n\nSo a 2K2 resistor - or 1K8 for a bit brighter would be your answer here (for the number of LEDS and type), rated at 2W or better.\n\nAs I said at the beginning, if ONE step of this doesn't make GOOD sense to you, PLEASE leave WELL alone.\n\n\n\nPLEASE DO NOT use this as a way to hook up the leds exactly as shown WITHOUT first checking their "forward voltage losses", I have used typical examples, different models can vary considerably.
146650
If you can get your hands on a solution of silver nitrate, it should be pretty easy.\n\nYou'll need a battery (9 volt should do it) and two lengths of wire.  Run one wire from the positive terminal of the battery and attach it to a silver electrode (available in science shops) or any piece of silver.  If you can't get the silver electrode, just use the copper wire.  This will plate some of the copper onto the ring, though.  Attach the other wire to the ring and to the negative battery terminal.  Lower the ring and the silver electrode into the silver nitrate solution (without letting them touch) and wait.\n\nThe positive silver ions in the solution will be attracted to the negative ring and should plate the ring nicely.
98657
This is stuff I have not worked with in 20 years. LOL. I can not draw this for you here, you can figure it maybe from what I tell you. \n(1) You want a circuit that has say 10V steered to four outputs depending on the control inputs. We will say the control inputs are 0 & 5 volts we are steering 10 volts. You are looking at a circuit with 7 lines. 1 input, 2 control and 4 outputs. The voltage to your controls has 4 possibilites.\n0&0 control volts input 10 volts to output line #1\n0&5 control volts input 10 volts to output line #2\n5&0 control volts input 10 volts to output line #3\n5&5 control volts input 10 volts to output line #4\nThat about all I can say here. May use AND, OR, NOR Gates??\n(2) Is even more complicated and I can not even begin to tell this in words. Hope this helps, I doubt it will, but, I tried.
297311
Item List:\n\n1. Potato \n2. Plate \n3. 2 pennies \n4. 2 galvanized nails \n5. Three(3) 8 inch lengths insulated copper wire, each with 2 inches of the insulation stripped off one end \n\nHow to do it\n\nFirst, cut a potato in half and put the two halves on a plate so they stand on their flat ends. The plate is there to keep your table clean. Then, wrap the end of one piece of wire around a galvanized nail and wrap the end of a second piece of wire around a penny. Stick the nail and penny into one half of the potato so that they're not touching each other. Next, wrap the third piece of wire around the other penny and put it into the other half of the potato. Put the other nail into the second half of the potato, but this nail should not have wire wrapped around it. Now, connect the wire from the penny on the first half of the potato to the nail that has no wire on it in the second half of the potato. Finally, touch the free ends of the wires to the battery section of the item you are trying to power. One wire goes to the positive(+) connection and the other wire goes to the negative(-) connection.\n \nDoes it work? \n\nYou'll probably have to try connecting the wires to the item in different ways to get the energy to flow through it in the right direction. It's just like putting batteries into a clock; they have to go in the right way.
54038
try http://www.audigys.gr  .I know they sell some good lighting lamps and effects from Element Labs. They have a bendable tube (clear in color) which when attaching a power source in it's side gets the tube lighten up in any color you choose! It is also ideal for creating any shape you like! Best news is that it's not expensive stuff.\nAudigys are in Athens, Greece but they are able to handle foreign orders very well and are very friendly people.
12550
If you are into electrochemistry you could make your own solar cell or a flat panel solar cell. A solar cell is a device for converting energy from the sun into electricity. This project is fairly easy and there are plenty of pics to show you exactly how its done. \n\nAlso read the first source listed first because it tells you things you need to know for the second experiment.
412256
build a simple 555 alarm circuit. Search yahoo with "555 IC"
213901
I prefer you buying one.  But there are always schematics out there that show you how to create your own inverters.  \n\nhttp://www.aaroncake.net/circuits/inverter.htm
433887
light duty is the problem - would be very easy to make one using any push on connector in the circuit ( you need a spring loaded connector with the pin being non conductive - a 'blade' shaped pin would be the easiest to rig )\n\nanother possibility is to use a switch of any type ( a - b ) that shunts the circuit to a open   circuit  ( this can be activated by a pull - and switched back manually )