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Author Topic: voltage reducer v resistors  (Read 7084 times)

g6swj

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Re: voltage reducer v resistors
« Reply #25 on: November 03, 2016, 07:08:28 PM »

If it looks like this then it's 200,000 ohm's (200K) - the second image is 200 ohm
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NFMike

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Re: voltage reducer v resistors
« Reply #26 on: November 03, 2016, 07:28:33 PM »

this is a picture of the resistors I got from Maplins, I  told the guy what I was doing and that I needed a 200 Ohm resistor this is what he sold me, the battery pack is giving me 7.68v, when I put it through the resistor it gives 6.40v and the 2 AA batteries give 3.13v, I must be doing something wrong but not sure what

Are you just connecting the resistor to one terminal of the battery pack and then your meter from the other battery terminal to the loose end of the resistor?

Subculture

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Re: voltage reducer v resistors
« Reply #27 on: November 03, 2016, 07:38:39 PM »

Running them in series requires current limiting just as much as parallel. 

So if you have four white LED's wired in series fed from a regulated 12 volt supply, what value resistor do you use?

Gopher

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Re: voltage reducer v resistors
« Reply #28 on: November 03, 2016, 08:38:36 PM »

sorry for the delay in getting back, G6swj it's the top one, red, black, black, orange , brown. is it right or wrong?  Plague, pretty much, I have tagged into my feed for the voltage reducer that powers my nav lights and exterior lamps and finally Subculture, I am probably wrong but if you have 4 white led's in series you would need 13.2v, some one on here will know for sure
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g6swj

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Re: voltage reducer v resistors
« Reply #29 on: November 03, 2016, 08:51:11 PM »

Gopher - The resistor you have is 199,800 ohms more than the one you thought you where buying - it is 200,000 not 200 OHM!!!

So I think another trip to Maplin may be on the cards...

Suggest you print off one of the many resistor colour code calculators from the net eg http://www.hobby-hour.com/electronics/resistorcalculator.php
and take it to Maplin so you can confirm what you are getting before leaving the store. Must be frustrating - stick with it - we are all learning from your journey :)

Regards
Jonathan



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Gopher

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Re: voltage reducer v resistors
« Reply #30 on: November 03, 2016, 09:01:26 PM »

this might sound a bit daft but if it was that much higher than I needed why didn't it wipe my voltage out, it only dropped it just over a volt
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Stavros

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Re: voltage reducer v resistors
« Reply #31 on: November 03, 2016, 09:17:17 PM »

Oh WHY oh WHY have you not contacted Component shop and simply tell them what Led's you bought off them and the voltage you are using and they will sell you the PROPER resistors.......................Maplin's I simply wouldnt give them time of day with resistors as they dont know what they are doing let alone selling........Young spotty nosed kids just out of their nappies.


Was in the local Maplins on monday and a customer wanted a charger for a 12v 10amp lead acid batt  and the young kid tried his best to sell him a car batt charger that was rated at 12amps I simply laughed and told him DONT and had to show him the correct charger that they sold ......THATS how GOOD they are NOT






Dave
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g6swj

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Re: voltage reducer v resistors
« Reply #32 on: November 03, 2016, 09:34:39 PM »

Dave,

Good suggestion re CShop - but you don't learn squat - half the fun is working through "it doesn't work" to "yeah I did that" - and that's where the learning comes from, not just for the individual but the many "silent" forum users.  There are lots of people on here as you know who could answer this without batting an eyelid.

So Gopher which ever route you take do let us know how you get on.....

Regards
Jonathan

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Stan

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Re: voltage reducer v resistors
« Reply #33 on: November 03, 2016, 09:43:38 PM »

HI Gopher did you order the resistors that put on the sketch I sent you last week? The value on the sketch were 195 ohms nearest value to this would have been 200 ohms, I have included some pictures of my latest wiring in my new fishing boat. If you use the formula in the C/Shop book you will have no problems.

stan
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Gopher

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Re: voltage reducer v resistors
« Reply #34 on: November 03, 2016, 09:47:07 PM »

I like to try and work things out if poss that's why I ask daft questions, but I think I will contact  the c-shop need a few more bits and let them supply the right gear, I will prevail one way or another
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Gopher

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Re: voltage reducer v resistors
« Reply #35 on: November 03, 2016, 09:49:54 PM »

Stan, I told the guy what I wanted, he sold me the wrong ones
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g6swj

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Re: voltage reducer v resistors
« Reply #36 on: November 03, 2016, 09:52:20 PM »

I like to try and work things out if poss that's why I ask daft questions,

The only daft question is the one you didn't ask!
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Stan

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Re: voltage reducer v resistors
« Reply #37 on: November 03, 2016, 09:57:35 PM »

Sorry to hear that you were sold the wrong ones lets hope when the new ones arrive this will sort out the problems you have had. I have  posted some pictures for you to have look at hang there all will come good.

Stan.
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malcolmfrary

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Re: voltage reducer v resistors
« Reply #38 on: November 04, 2016, 10:21:44 AM »

If you took your voltage readings without the LED in circuit, the very small voltage reduction is about what would be expected with a high resistor value dropping the current that the meter could read from.  If the LED was in circuit, the very high value of resistor might well limit the current below the level where the LED could properly switch on and show its expected properties.  The reading might well be just the effect of trying to read the voltage through a high value resistor.
With the correct value, you will get the right results.  Like I said earlier, you need to read the current drawn when the LED is fed by the voltage source and calculate the resistor value for the 7.2 volt source accordingly.  But 200Ω sounds about right, provided the store assistant can tell the difference between brown and orange, or K and Ω.
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Gopher

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Re: voltage reducer v resistors
« Reply #39 on: November 04, 2016, 01:42:56 PM »

Going to order some more bits from c-shop I will talk to them and sort out what I need
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RAAArtyGunner

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Re: voltage reducer v resistors
« Reply #40 on: November 04, 2016, 11:23:40 PM »


Gopher, off subject Trivia.
I take it that Mansfield is in the UK.
Because there are two Mansfield's in OZ.
One in the state of  Victoria, a country town, The other in state of Queensland, a Brisbane suburb.
This would then make you an ornery Oztralian.
Back to boats.
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inertia

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Re: voltage reducer v resistors
« Reply #41 on: November 04, 2016, 11:28:06 PM »

There is only one true Mansfield.
Believe me.......
DM
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RAAArtyGunner

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Re: voltage reducer v resistors
« Reply #42 on: November 05, 2016, 12:35:18 AM »


Correct,  O0 O0 the one in Brisbane.  %) %)
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tigertiger

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Re: voltage reducer v resistors
« Reply #43 on: November 05, 2016, 07:52:58 AM »

No, the one in Monte Carlo  ;) :o
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Kipper

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Re: voltage reducer v resistors
« Reply #44 on: November 05, 2016, 11:56:27 AM »

There is only one true Mansfield.
Believe me.......
DM

If it's still the same as when I resided there in the early 80's ................... thank god there is only one.  :-)
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Colin Bishop

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Re: voltage reducer v resistors
« Reply #45 on: November 05, 2016, 12:02:57 PM »

Jayne....?
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inertia

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Re: voltage reducer v resistors
« Reply #46 on: November 05, 2016, 12:30:36 PM »

If it's still the same as when I resided there in the early 80's ................... thank god there is only one.  :-)
Nah. The rest of t'shops have since closed but t'sparrers still fly back'uds to keep t'muck out their eyes.... I doubt if there is any equivalent paradise in Oz; it's only been there a few billion years, after all.
For the benefit of our Oz cousins, Mansfield used to be a colliery town in North Nottinghamshire. The pits have long closed but it's still filthy-dirty and the rancour between the former members of the two rival pit unions still festers there. O, and they now have another Victorian employer who pays poverty wages and fines his slaves for going to the loo. His name is Mike Ashley and he owns JJB Sports and some football club up north somewhere..... ;D
For what it's worth I always use resistors with LEDs, mainly because I have boxes of the things!
 DM
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Gopher

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Re: voltage reducer v resistors
« Reply #47 on: November 05, 2016, 04:13:40 PM »

Sports direct
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inertia

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Re: voltage reducer v resistors
« Reply #48 on: November 05, 2016, 05:39:46 PM »

Yep - you're right. I don't use either, not being the huntin', shootin' and fishin' type (are there any of those old duffers left??).
He's still a thoroughly nasty piece of work, though.
The folk of Shirebrook deserve better.
DM
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Gopher

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Re: voltage reducer v resistors
« Reply #49 on: November 05, 2016, 09:35:17 PM »

Got a lot of family in Shirebrook, it' like a mini eastern block state now, it's full of polish, Latvians and so on all working at sports direct
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