Matt B Posted May 21, 2009 Share Posted May 21, 2009 If your scared of the maths, then why not use an Ohms law calculator? Just put in the values you have (i.e excess voltage, and the amount of current being drawn) and it will work out the resistor value for you? Quote Link to comment Share on other sites More sharing options...
Aterlatus Posted May 21, 2009 Share Posted May 21, 2009 OK, to clarify exactly how the resistor limits the current.... Remember in secondary school when you worked with Ohms law in Physics? Ohms law is your friend. Voltage = Current x Resistance Now because we know what voltage is, and the resistance of a resistor is constant (within reason) we want to rearrange that formula. Current = Voltage / Resistance As the resistance of a circuit increases, the current it will carry decreases. That's the whole idea of a current limiting resistor. Without it, you have a closed loop with very little resistance. With it, you have a closed loop with a moderate resistance which prevents the current getting too high. Stick a wire across the terminals of a battery and you'll notice it gets very hot. Stick a resistor over it and you'll notice it doesn't get hot at all (unless it's a REALLY low value!). Quote Link to comment Share on other sites More sharing options...
Merlin Posted May 21, 2009 Share Posted May 21, 2009 Does this lot mean when my badger hits 88mph, i'm gunna go back to the future? 1 Quote Link to comment Share on other sites More sharing options...
Aterlatus Posted May 21, 2009 Share Posted May 21, 2009 I'm not sure a 6v hump pack can supply 1.21 gigawatt.... best make it a 7.2v eh? Quote Link to comment Share on other sites More sharing options...
Merlin Posted May 21, 2009 Share Posted May 21, 2009 no problem. Quote Link to comment Share on other sites More sharing options...
Aterlatus Posted May 21, 2009 Share Posted May 21, 2009 Don't forget to pronounce it "jiggawatt" when you're talking to people as well. Otherwise you won't sound like a mad scientist. Quote Link to comment Share on other sites More sharing options...
perruzo Posted May 21, 2009 Author Share Posted May 21, 2009 (edited) Merlin - what size flux capacitor did you use on your reactor? And where did the "scared of maths" come from in the other posts? i did it at A-level for my HND years ago. Not scared - just can't be bothered with it - i hate maths, nothing like a dose of calculus or transposition in the morning to pick you right up....not Edited May 21, 2009 by perruzo Quote Link to comment Share on other sites More sharing options...
Aterlatus Posted May 21, 2009 Share Posted May 21, 2009 (edited) so in a short circuit situation this resistor is going to protect the rest of your baja?. surely if/when shorted it is capable to pull an awful lot of current through that resistor - you mention 10amps - surely then this would overheat the wiring and cause the very burnout we are trying to avoid or would the resistor sacrifice itself? Just in case I got a bit too technical in the earlier explanation for anyone I'll clarify a bit here - the resistor stops the current from shooting up during a short. It doesn't sacrifice itself to the current - it just stops the huge current from flowing in the first place. If it's unclear to anyone then feel free to ask me any questions - in case you couldn't tell I like to talk electronics... Edit: And stop trying to take everything personally perruzo. When I post in these forums I keep in mind that they're indexed by search engines, so tend to talk to the wider audience rather than directing everything at one person. When I say "if you're scared of the maths" I'm not talking to you specifically, more a general statement for other readers. Edited May 21, 2009 by Aterlatus Quote Link to comment Share on other sites More sharing options...
Merlin Posted May 21, 2009 Share Posted May 21, 2009 Thats mine Quote Link to comment Share on other sites More sharing options...
Aterlatus Posted May 21, 2009 Share Posted May 21, 2009 I've got some 'fluxxed' capacitors if anyone's looking to buy. Quote Link to comment Share on other sites More sharing options...
Matt B Posted May 21, 2009 Share Posted May 21, 2009 I've got some 'fluxxed' capacitors if anyone's looking to buy. Oh dear I'm still after buying a few 1 farad caps from maplins to make a very dangerous low voltage, high current circuit at some point Quote Link to comment Share on other sites More sharing options...
Aterlatus Posted May 21, 2009 Share Posted May 21, 2009 I prefer high voltage low current. Much less deadly. So if anyone has a neon sign transformer they aren't using... Quote Link to comment Share on other sites More sharing options...
Hiks Posted May 21, 2009 Share Posted May 21, 2009 (edited) I know how that happened! You told me the whole story. You were standing on your toilet, and you were hanging a clock, and you fell, and you hit your head on the sink. And that's when you came up with the idea for the Flux Capacitor... When I post in these forums I keep in mind that they're indexed by search engines, so tend to talk to the wider audience rather than directing everything at one person. Martin Luther King style! I like it. Edited May 21, 2009 by Hiks Quote Link to comment Share on other sites More sharing options...
Matt B Posted May 21, 2009 Share Posted May 21, 2009 Just as fun, might have to look them up on the bay Quote Link to comment Share on other sites More sharing options...
bodgemonkey Posted July 13, 2009 Share Posted July 13, 2009 is it just me but everytime time you lot mention flux capacitator i think of a HPI savage that can travel through time? Quote Link to comment Share on other sites More sharing options...
perruzo Posted July 13, 2009 Author Share Posted July 13, 2009 aaargh the dust, its in my eyes, blinding, cant see...... Quote Link to comment Share on other sites More sharing options...
Hyper-d Posted August 30, 2014 Share Posted August 30, 2014 Sorry to drag up an old thread but I made myself a set of light pods after reading this thread, only difference being I added a resistor to the positive rail on both pods. Problem I'm having is one pod is brighter than the other, any ideas why? Thanks Quote Link to comment Share on other sites More sharing options...
Tamiyacowboy Posted August 30, 2014 Share Posted August 30, 2014 so two light pods but one is more dull. yes one reason only for this to happen. your powering both pods from same battery, lets say they work awesome on 9v and 1 pod. but when you add a second one is duller than other, what this means is you have a voltage sag now adding a capacitor can help but not much at all, the better option is either up the voltage with risk to the light pods being overpowered or to run two seperate batterys. the problem is to many leds for the amount of voltage you have on tap. the second problem is closed caps. now your light pods really need to be chromed and polished out, this will act as a reflector. and it means your able to collect all side thrown light and direct it forwards, running a single cree smd led at say 1w in a reflecting pod will be 100X better than a group of say three in a none reflecting pod. now light is counted in lumens, the sun 120,000+ lumens , your standard eco bulb in house 1,100 lumens lumens is the amount of light given. you need to work out what you require and then how many volts it will take to give that. now a simple way is to make a test block, you can add the voltage at one end, and the railing system allows you to push in your led's, this will give you a light rail but also allow you to see how many bulbs your powersource can light up without much of a drop in lumens, ( the futher up the led rail you go the less bright leds will be you remove them untill the rest of the leds are the same brightness this is the max number of leds that battery will sustain at a decent output.) Quote Link to comment Share on other sites More sharing options...
Hyper-d Posted August 31, 2014 Share Posted August 31, 2014 Thanks for a very informative reply might try running off a 9v to see if that helps Quote Link to comment Share on other sites More sharing options...
RCbutcher Posted August 31, 2014 Share Posted August 31, 2014 That's great info from tami and explains why a lot of people leave 1 or 2 leds out on each pod. I've been battling the same thing but haven't orderd the pcb disks yet. Quote Link to comment Share on other sites More sharing options...
RCbutcher Posted August 31, 2014 Share Posted August 31, 2014 I've just knocked one up for testing. I was waiting to find pcb boards and some safety components but now I've seen this I thought ide give it a shot. I've done it the same way as p1 then lifted the led clump out the pod to later power it from 6v then 9v. This is powerd in series tho isn't it I prefer parallel for ease. Quote Link to comment Share on other sites More sharing options...
Hyper-d Posted August 31, 2014 Share Posted August 31, 2014 (edited) I've just knocked one up for testing. I was waiting to find pcb boards and some safety components but now I've seen this I thought ide give it a shot. I've done it the same way as p1 then lifted the led clump out the pod to later power it from 6v then 9v. This is powerd in series tho isn't it I prefer parallel for ease.What LEDs are you using? I'm using 15000 mcd 3.2v, can't remember what the resistors are but I did use a resistor calculator thingy to get the right ones (I think) lol Edited August 31, 2014 by Hyper-d Quote Link to comment Share on other sites More sharing options...
Tamiyacowboy Posted August 31, 2014 Share Posted August 31, 2014 always a good idea to add in a resistor set. More is better, thats what you would think, but in leds its not about the amount its about the maximum to use for a given need. those arduino breadboards, white with lotsa holes in. use one or two of these and pop you leds into the rails, hook them up to juice and have a play, the breadboard acts like a plugnplay unit. we can add switches, toroid coils, regulators. Regulator: and use in electronics. now your lights are hooked to the battery direct via wires, so that 9v battery gives all its 9v. as your lights suck the electrons from the battery the voltage starts to wobble up and down, we call this an unregulated power driver, as the voltage of the battery slowly goes down you will notice an led dimming, more voltage drained a the led goes out and another starts to dull. overtime you end up with a few leds but hardley no photons. now a regulator has three legs, a gate - a drain - a tap ( gate is inputvolts and can be as high as 30v or more, drain is our ground/earth and tap our output ) i put a regulator into the system, its a 30v to 5v, that means upto 30v in, but it will only let 5v out, when the voltage gets to low the device will not work so your lights stop working. same thing is in your esc thats how you get the 5v reciever power, the same small device is in your ubecs and likes. it takes one voltage in and gives a fixed voltage or what we call a regulated voltage its always going to be 5v unless the battery drops below 5vs. another way is pulsing the leds at a very high hz, this rapid on and off saves battery use and extends the time the lights run for. to a human eye the led stays alight constant, but reality it blinks so fast we cannot tell. this is how your solar garden lights work of a single aa battery, with clever thought and use of items you can run 300 leds from a single DEAD aa battery. what you need to look at is making your lights for a given job, whats the use of 4000 lumes kicking out if your not going to use them and just waste the photons produced. so think this the angle the led throws out light less degrees = a more narrow beam and less waste on side cast light. and maybe look at regulating the input power to fixed 6v, but upto 12v input via a regulator. add a simple small MC chip and even more leds you can do this. you can also make charlieplexed light rails. Quote Link to comment Share on other sites More sharing options...
RCbutcher Posted August 31, 2014 Share Posted August 31, 2014 Would a capacitor be enough for the small voltage were using here tho. For the resister it would be an ache soldering in a res in front of each led could one or two resisters be used instead like put one as the link from the out pairs to the rails with heatshrink on them just as this is shown with wire. Or just put one on the pos battery wire before it exits the pod. I've made two now and feel comfortable making the circuit now so I will go to refining now. These are working pretty well tho but I haven't had them on for hours yet. The first clump I did had two dud leds in the centre I think I didn't link them well enough the 2nd clump is all on tho and 10x neater. I have a bread board/jig for making the circuits it definitely helps but you could do it as here and use the pod face plate then push them out. I'll find my volt metre tomorrow and see what that says and go from there. I've seen those 3d led cubes they are crazy cool there's some huge ones on youtube running aurdrino making like firework displays. Aurdrino is cool I want to get into that at some point. Quote Link to comment Share on other sites More sharing options...
RCbutcher Posted August 31, 2014 Share Posted August 31, 2014 These are the cubes I saw when looking through aurdrino it's amazing but way out of my range but mayb one day. http://m.youtube.com/watch?v=3K8i0JQzx2w Quote Link to comment Share on other sites More sharing options...
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