### Resistance is Futile

Do you agree with the saying, Resistance is Futile? It can be applied in anything, politics, electronics, etc.

Topic by starwing123   |  last reply

### capacitor resistance

Why is it that as super capacitors capacitance goes up the internal resistance goes down? I'm looking for a tiny capacitor that can supply 0.3 volts20mA (I'm going to be powering flexinol, not an LED) for 1 second. I don't want the capacitor to be huge because I'm making a beam bot where size is a factor for charging time and because of it's physical size.

Topic by guyfrom7up   |  last reply

I was wondering when i wire LEDs together does there have to be a resister for every LED? (i making an arc reactor with 7 LEDs)

Question by Emsaid   |  last reply

### Speaker resistance?

I have an amp schematics and for the speaker rezistance it says 8 ohms. I have 4 ohm speakers so I am worried that amp circuit will burn. Will it be ok, or should I put a 4ohm resistor in series with the speaker. The chip is TDA2615. Power source is 12v lead-acid battery.

Question by Dantex   |  last reply

### Help with Resistance formula. Answered

How to find the voltage after adding a resistor with the resistance formula? For example I have a circuit that uses 0.975A and I add a 1000ohm resistor to it, if its powered by 220v main then according to V=IR what should be the voltage drop due to the resistor?

### Simple Resistance Question

I am wiring some LEDs in series-parallel using a 9v battery. The schematic I've been looking at online as a reference shows resistors being used but doesn't say what size. Here is the layout: |-- LED -- LED -- LED -- resistor?--| |-- LED -- LED -- LED -- resistor?--| |-- LED -- LED -- LED -- resistor?--| |--9v-----------------------------------------| I assume it's a simple calculation but I haven't worked with this stuff in a few years. Thanks in advance.

Topic by L3fty   |  last reply

I recently got a new watch for my 18th birthday. On the back of it, it said "5 ATM". I looked it up, and supposedly it should be water resistant to 50 meters or 165 feet. However, all places I went to online said to only have it around sinks, "slight splashes", shallow water, and to not use it for snorkeling. I live near the ocean and would most likely use it for that; not for any real diving though. Shouldn't a 50 meter tested watch be able to handle a few feet of water, or is it because it's saltwater that it would not be able to?

Question by The Dark Lord   |  last reply

### How to calculate resistance?

Ok, I need to figure out how to know what resistor to use. I know how to read a reistor, I just dont know how to use one. Say I hook an LED, a 9 volt battery, and a resistor in a circuit. I want to get the voltage down to 3 volts. How would I go about calculating a resistor reading? What ohm resistor would I use? How do I know?

### LEDs in resistance sensitive circuit

My question is relative to getting a LED to function correctly in a resistance sensitive circuit.  Here is the situation. 1. The Battery Warning Light in an automobile I am restoring currently uses an incandescent bulb.  2. Functionally, the light is on when the ignition is turned on, but goes off when the engine starts.  3. This works fine with the incandescent bulb, but not with a LED, even if I put the same incandescent bulb in the circuit (parallel). 4.With just the LED in the circuit, it never goes off.  This is because the circuit has about .5V leakage voltage through the device (which is a Lucas 3AW Warning Light Unit) when the engine is running (and correctly, 12V when just the ignition is on). 5. With both the LED and the incandescent in the circuit, the incandescent does not come on and the LED does not go off, both with ignition on and engine running. 6. I have also put a potentiometer in the circuit with just the LED and cranked it from 1 Ohm to 100K Ohms, with no effect. 7. Of course, an easy answer is to just use the incandescent, except that the dash is wired and complete and installed, and I prefer to get the LED to work.  Any thoughts or suggestions would be very much appreciated.

Topic by DaleR18   |  last reply

### Really basic Resistance / Amperage question:

Before I begin: yes, I should know this already, but I'm really sleep deprived right now, and therefore slightly muzzy on my electronics knowledge... My circuit has two loops running in parallel off one, limited, 18v power supply: [*] Loop 1 requires the majority of the supply's power to run [*] Loop 2 is simply a 7805 voltage regulator supplying 5v to an analog input on an Arduino, so needs almost no current running through it. [*] when Loop 1 and Loop 2 are both active, Loop 1 does not get enough power. if I place a resistor in Loop 2, in series with the 7805, will it increase the amperage to Loop 1? I think the answer is yes, but, once again, I'm MASSIVELY sleep deprived. any help is appreciated.

Topic by gschoppe   |  last reply

### How to create motor or generator resistance system for exercise machine?

Researching a method to use resistance from a motor or generator for an exercise machine.  There is an axle from which both foot and arm levers extend, so there is rotation, but only about a half turn in each direction, so very low speed, and back and forth.  I have used magnets and eddy current and flywheel from exercise bikes, geared up with a belt.  This works ok, but does not provide enough resitance even when magnets are adjusted very close to flywheel (due to low speed of rotation). I hope to find something already built and available for a similar application, but can locate parts and build it if I understand how.  Resistance must be variable from low to very strong and controllable so user can adjust it.  I have DC motor, and shorting the cord greatly increases the drag, but how do I vary/control it?  Would adding resistance between the wires in the cord increase drag and make it harder to turn?  I have experimented with this and it does not seem to have an impact.  Thanks for your help.

Question by zanimann   |  last reply

### what is connection for variable resistance having 3. pin. pls tel me where supply and load connected.?

Question by vijaysinha   |  last reply

### Resistance calculator using flash

I just created a resistance calculator using liveswif (its like macromedia flash only not as good) and programmed it with actionscript.   I can't figure out how to get the numbers to line up properly, although the calculator still works.   If you have a resistor and need to find out how many ohms it is, the calculator will do it.   http://www.gamesfree4u.com/resistancecalculator.html

Topic by pennsteve   |  last reply

### Some help with Ohms and resistance? Answered

Hey guys, i know there are a lot of you guys out there that deal with electrical dealings and such, and im doing a science project, dealing with electrolysis, so i decided to compare two electrolytes to see which has a lower resistance, and to see which would be more efficient therefore. SO, the only problem is, i have no multimeter, voltmeter, or anything close to it, and i don't know anybody 'round her that does..So im asking you, could you help me with seeing the resistance of- * water (tap water) * water with Epsom Salts  * and water with Baking soda powder (either will work, but i would prefer powder, as baking soda is said to cause chlorine gas, and what not..whichever you have works) If you could take a picture of yourself using the multimeter, that would be stellar, thats all for now,  come on guys, i know you know this stuff, and i just cant figure it out, counting on you :)

Question by fwjs28   |  last reply

### what is rolling resistance in tire?

Question by thomasraja   |  last reply

Hi I'm looking for a natural, cheap water resistant adhesive that can be applied to plant matter Ideally soluble in hot water so it can be easily applied but insoluble in cold water. Any ideas?

Topic by Isjmarshall   |  last reply

### Natural Water Resistant Glue

Hi  I'm looking for a natural, cheap water resistant glue that can be applied to plant matter Ideally soluble in hot water so it can be easily applied but insoluble in cold water. Any ideas?

Topic by Isjmarshall   |  last reply

### is there a foodsafe and heat resistant adheisive?

I am joining copper tube to a stainless steel pot lid, i have joined them but want to make an airtight seal. is there an adheisive i can use that will be heat resistant and not react with alcohol?

Question by the rowdyboy   |  last reply

### how to make a resistant box?

I need an idea! I'm a magician and i want to create my magic bag. I thought that i can make the wood box with nails and after i can veneer it. The problem is that I never made anything in wood.  So the question is: is it a resistant box or not? do you have some advice? (Sorry for my english :S) thank you!

Topic by michele92   |  last reply

### D.C input resistance of a BJT transistor in C.E configuration?

What will be resistance across base and emitter of BJT in C.E configuration

Question by deepakmurali   |  last reply

### How UV resistant is wood? Answered

I'm making a USB solar charger intended to last 20 years. It will have no batteries inside, just a voltage reg and a zener diode. The solar cells will be wired together under glass, not epoxy (for better lifespan). I want the frame to be made of wood, but how long will that last in direct sunlight? This solar charger will contain no plastics, polymers, or resins...so my only choice for a frame is glass and wood. THANK YOU SO MUCH!! -Nepheron PS. I chose wood because it is very opaque, and I reasoned that it may be fairly UV resistant... But IDK.

Question by nepheron   |  last reply

### Resistance Isn't So Futile

Nissan has introduced the Eco Pedal, an acceleration pedal that pushes back on the driver's foot if the driver is supplying unnecessary pressure and therefore being fuel inefficient. From Wired News: Nissan estimates that the Eco Pedal, coupled with the already ubiquitous instant fuel readout on the dash, can increase fuel economy 10 to 15 percent.While it may hinder driving freedom a little bit, it seems more like it's there to be a friendly little reminder. Sort of like parents when you're learning how to drive. Very environmentally friendly, fuel optimizing parents. Nissan via Wired News

Topic by joshf   |  last reply

### Inductance and resistance question help

Topic by Andrew187   |  last reply

### Antibiotic resistance and factory farming

Topic by canida   |  last reply

### How to add magnets to magnetic resistance exercise bike to increase resistance?

Hi, and thanks for reading my question.      We have just bought an exercise bike, it uses the pedalling to power the magnetic resistance of the bike. Here is the problem: at the highest setting, the resistance is still not very much.  We think that maybe we can increase the resistance by putting a strong permanent magnet near the flywheel, (we would cut a hole in the plastic cover to put the magnet near the flywheel). Can someone explain how to figure out how strong a magnet would need to be? How much "pull" would probably have a significant effect? What type (neodymium?), and what shape would work best (disk, rod, etc...?). We are willing to put about \$50 into a magnet.   If this doesn't work I think I will remove the cover and just use a "friction wheel" sitting on top of the flywheel. really ugly, but it should work. Thanks for any help you guys can give!

Question by Urrgghh004   |  last reply

### How to control the Voltage, Current and Resistance in a circuit?

I've seen devices which do this but I don't know the name of it?

Question by ShanL3   |  last reply

### New Antibiotics.

Antibiotic resistance is becoming a real problem, and I figured that the crafty and scientific community could help. https://petitions.whitehouse.gov/petition/help-fund-and-add-incentive-drug-companies-create-new-and-better-antibiotics-fight-rising-super/nwTTbVX3 I started this petition on the white house website. Note: This is at no benefit to me, I am just trying to bring awareness to this issue.

Topic by airsofter1   |  last reply

### How does one make a reverse photocell?

How can you use a photocell to make a circuit whose resistance is proportional to incident light? I'm looking for an open circuit in the dark and a short circuit in lighted conditions.

Question by EEWolverine   |  last reply

### reducing current on a power supply

So I am trying to reduce the on the current power supply I have from an old router. The out put is 12v DC 800mA (.8A). I want to use it to run a man 12v .3AI just wanted to make sure I did my math right and to make sure I didnt miss anything.Ohms LawI = V/RR= V/I V = 12 I = .812/.8 = 15 ohms resistance in theroy_Current on the fan is .3 A, I am assuming that is the max. So desired current is .25I = .25 V = 12 R is current resistance, X is additional resistance Q=(R+X)I = V/QQ= V/IR+X = V/IX = (V/I) - R V = 12 I = .25 R = 15(12/.25) - 15 = 33 ohm resistance neededSo I would need a minimum of 33 ohm resistor. Am I correct?Sorry for the explicitness of the math, its been drilled into me to show every step.

Topic by dragonkeeper117   |  last reply

### what type of resistor should i use if i have 3 of these LED's in a series with a 12v batter?

LED Specs Size (mm) : 5mm Lens Color : Water Clear Reverse Current (uA) : <=30 Life Rating : 100,000 Hours Viewing Angle : 180 Degrees Absolute Maximum Ratings (Ta=25°C) Max Power Dissipation : 80mw Max Continuous Forward Current : 24mA Max Peak Forward Current : 75mA Reverse Voltage : 5~6V Lead Soldering Temperature : 240°C (<5Sec) Operating Temperature Range : -25°C ~ +85°C Preservative Temperature Range : -30°C ~ +100°Cï»¿ and i'm using a B3v-250c   3 LED array to hook them up that i bought from ebay

Question by JustXtreme   |  last reply

### Help finding adjustable and slip resistant material!

I am working on a project where I want to be able to paint with 5 brushes of different sizes simultaneously. For this, I need to build a device that can hold 5 paintbrushes together, one next to another with a 0.5 inch gap between them (so the bristles don't overlap). My challenge so far is to find a clamp or material that can adjust to various sizes of handles while keeping everything still when I push down to paint.  I have tried to poke the brushes through a piece of foam but they will slip and go through (depending on the shape of the brush). Someone suggested duct tape but I'd like this device to be reusable and easy to change between brushes.  Basically, can anyone suggest an adjustable clamp or some better material that can fit various diameters and hold still?

Topic by Julep   |  last reply

### cutable laser?

I know scientist have created lasers that can cut but how much money would it take to make one? and what materials would be need? and... what kinds of materials would be laser resistance, not effected by a laser... or would that depend on the lasers stength?

Question by saiyankev   |  last reply

### Must have capacitors, resistors, transistors

I am wanting to know the best values/ most used values in electronics projects for resistors, capacitors, and transistors. Suggestions? Also when purchasing capacitors, ceramic vs. electrolyte? Are ceramic mostly for lower capacitance values? And lastly what is the difference between a 10k resistor and a 10 Ohm resistor. What I have figured out is that the 10k is a higher resistance value.  Thanks, diamondmine

Topic by diamondmine   |  last reply

### Diode question

I need help with diode. Actually a question: if you put diodes in series for example 2 diodes of 300 V will they act as one diode of 600 V?

Topic by Dantex   |  last reply

### LEDs and resistors

I notice a lot of people tell you to always put a resistor on an LED. Should I use a resistor if my LED's forward voltage is the same as my power supply?

Topic by bomberman3   |  last reply

### What do 1/4, 1/2, 1 or 5 watts values mean on a resistor? Answered

I know that this is such a basic question but what do those values mean when selecting a resistor?

Question by blkhawk   |  last reply

### Dimming Leds and Potentiometers

Looking for a formula; I have a 24v 1.7 amp power supply ( http://www.allelectronics.com/make-a-store/item/PS-2417/24VDC-1.7A-POWER-SUPPLY/1.html ) to light 2 - 24v led strips ( http://www.allelectronics.com/make-a-store/item/LBR-24/24-WHITE-LED-LIGHT-STRIP-24VDC/1.html ). I want to be able to dim the led's from full power to completely off, but don't know how to calculate what size of potentiometer would give me the right ratio for dimming. IE, I don't want the LEDs to be completely off when the pot is only halfway turned. The urls are links to the exact products I purchased. Also, the power supply seems kind of large, and I still have to enclose it, so if anybody knows of a better and cheap path to get 24v that involves a little less potential for death, I'm all ears. Thanks!

Topic by bctour7   |  last reply

### Why are sharpie pens acid resistance? Answered

What's the chemical compound of the sharpie to make it acid resistance? Such as for PCB etching.

Question by nfarrow   |  last reply

### What is the internal resistance of a 9V battery? Answered

Question by Yashknowsbetter   |  last reply

### Good motor for providing bike resistance? Answered

I would like to use a motor to provide a variable bike resistance.  The bike will be turning the motor, and the motor will provide a physical resistance, making it easier or harder to pedal.  My ultimate goal is to make a microprocessor-controlled stationary bike, where the micro can both set the physical resistance of the motor and detect the speed of the motor.  My intention is to use a variable electrical resistance to make the motor harder or easier to turn.  However, I don't know much about motors, so my question is: what kind of motor will work for this?  Any comments welcome.

Question by FazJaxton   |  last reply

### How to calculate the equivalent resistance of this circuit? Answered

I WANT TO KNOW HOW TO CALCULATE THE TOTAL RESISTANCE OF THIS CIRCUIT ! I CAN'T FIGURE OUT WHAT THE RED MARKED RESISTOR PLAYS CAN ANY ONE PLEASE EXPLAIN?

### Looking for Heat Resistant Flexible Material

I am trying to find a heat resistant material that is flexible... I am trying to make a pull down shade to attach to a tension rod, that will make my home more energy efficient... This means It will also need to be thin enough to roll up into a small roll... It needs to be reflective or at least block out all the sun... I work nights and sleep through the day, and have trouble sleeping when the sun gets through...

### Is there a way to lower a photocell's resistance to amps? Answered

I am making a device which uses a laser to lower a photocell's resistance to the point where enough current can flow to begin spinning a motor. Unfortunately, the motor (4.5 V) starts off by drawing about .75 amps and once running falls to .25 amps, but apparently the photocell can only draw a lot less- the only word I've been able to find is that it typically draws about 1 milliamp, which is nowhere near enough. I have two questions- first off, does anyone know how many milliamps I can run through a photocell, and is there any way that is pretty cheap so that I can lower the amps drawn or the resistance of the photocell without stopping the motors?

Question by seraine   |  last reply

### are capri sun pouches UV resistant?

after reading the capri sun welding instructable i was thinking of making an outdoor tarp out of them to cover my lawnmowers. maybe even putting it on the roof in summer to reflect heat and reduce cooling costs. my kids love these things so i have a lot of them.

Question by dannemillerd   |  last reply

### Electric Power Generation and Resistance Questions

Okay so I understand the basic concepts of power generation but I have a question pertaining to the old addage: An object in motion tends to stay in motion. Resistance is power that stops any said object if it is equal to the energy of the object in motion - this resistance is from gravity and other outside forces acting upon said object. OKAY If the force to put an object in motion was then then collected by electrical generators from multiple other sources as part of the same object - would it be able to make up for the amount of resistance from the added collection and the amount needed to put said object into motion and keeping it in motion???? If an object is designed to be in motion then it does not require as much energy to stay in motion as it does to be put in motion. Even when affected by gravity, as it is affected by gravity less when is in motion. But can technology (bearings and rotors) be designed so they offer less resistance than the amount of energy required to keep said object in motion? This is impossible as far as I am aware. Energy is NOT free - but If the energy required to keep an object in motion is less than required to put it into motion, would not the true energy of the object in motion be greater than what is required to keep it in motion and be able to be collected as excess energy? Collection would result in resistance however and since the formula of "greater or equal force" applies collecting anything other than that differential in energy would result in the objects motion being slowed. Is this true? I am concerned about going into details on the nature of my concept until I can gain a better understanding of the science behind it. As such I apologize for how vague my questioning is.

Topic by Tetsuoh   |  last reply

### Add resistance to a led tail light?

I have a Led Tail light to wire to my motorcycle. I split my running light to light up my flashers also. My question is how can I make my tail light less bright? I off course think about putting a resistance, but how to choose the right one?here's my spec:12V motorcycle batteryLed light: 15 white LEDs2 flashers: 12 volts incandescent bulbsWiring: original running light split in two (1 in tail light and one to the back) then the second one split into the two flashersThank you all

Question by JimmyM95   |  last reply

Hi, my name is david. im working on a project, for a device that is roughly .25-.5 inches long. im trying to find the right material resistance wire for the application. the components are submerged in coolant to maintain a low temperature. i wish to have a resistance wire of some kind wrapped around the components to heat them to about 90 degrees as quickly as a possibly can, for only a brief time(fractions of a second) i am using a variable power supply to determine my power needs. im hoping to be able to send a quick "signal" through the resistance wire, and use heat as a sort of input/output system. the internal components will melt at temperatures above 100 degrees.  so regulating the temperatures is key.  now obviously since they will be submerged in coolant, the resistance wire will need to heat to higher temperatures in order to heat the other components. ive been doing some research on nichrome and kanthal wire. but from what ive seen so far, it almost heats up to quickly, to higher temperatures than i require. it is hard for me to do the calculations, since i dont know how many watts/amps etc i will be using.  so to recap: temperature required about 90 degrees. (as quickly as possible, "flash heating" to 90degrees would be great) length is .25-.5 inch (the size will actualy be determined by the resistance wire i would prefer it to be as small as possible but i could make the module larger if i have to) variable power supply to determine my power needs(preferably the lowest possible power usage to conserve battery power) any suggestions on an appropriate material would be appreciated. i dont mind testing out different materials. i just dont want to spend thousands of dollars buying a little bit of everything and testing each one out one at a time. >< some experiments have suggesting silver coated nylon, but requires 20watts and a pretty sizable heating time. the heating coil will most likely have direct contact with the components, unless it is required to provide space between the coil and the components to heat it appropriately. i would prefer direct contact though to make the modules as compact as possible. currently the coolant is being pumped continuously through the whole system, but ive been working on plans for a valve to interupt the flow of the coolant during cycles where the coil is activated, if the need arises to keep the coolant from preventing the resistance wire from heating up appropriately.

Topic by DavidW433   |  last reply

### small hobby resistance/spot welder?

I want to weld small steel wires (the size of guitar strings - +/_ .035) to make small sculptures. Solder works, but is not fast or strong enough. Can I make a welder to run on 115VAC?

Question by Dweevil