mkblade
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| posted on 14/5/09 at 10:50 PM |
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wiring in 390ohm resister
hi all
been to maplins tonite to get the above resistor (see pic) it look a lot different to what i took out at the weekend.
my one is the red one and the blue one is from maplins i asked for a 390ohm resistor and after 10 mins of scatching his had looking puzzled he gave me
the resistors.
first of all they look to small ,and how do i test them to see if they are right i know with a multimeter but thats about it.
i know they should only go one way round,i would really like to check the red one which i took out of the car to see if its working .
thanks in advance
simon.jpg)
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mkblade
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| posted on 14/5/09 at 10:51 PM |
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a bigger pic (Small).jpg)
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blakep82
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| posted on 14/5/09 at 10:51 PM |
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picture won't load up, but they should have coloured bands painted round them. i forget how the colours work, but they should be the same, in
the same order. if they are then its the same resistance
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Steve Hignett
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| posted on 14/5/09 at 10:55 PM |
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Resistors can go any way round (Diode's are "handed)
[Edited on 14/5/09 by Steve Hignett]
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blakep82
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| posted on 14/5/09 at 10:55 PM |
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multimeter will work fine. they can be connected either way around. i wonder if he's given you 2 smaller ones with the same total value as the
big one? can't see the colours well enough. can't remember how they work either
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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brianthemagical
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| posted on 14/5/09 at 11:02 PM |
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They are about as simple as electronics get. Put your meter across them, in Ohms, they are not polarised, and see what they say, should be about 5%
difference max.
The size difference is down the power rating, or heat capacity if you like. Looks to be at a watt or so, you ones you bought are an 1/8th watt i
think. they will likely die. Where did it come form and what's it used for?
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splitrivet
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| posted on 14/5/09 at 11:25 PM |
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Hard to tell what the value is of the resistors they sold you but they dont look right.
Maplins part code for what you need is D390R which is 2 watt metal film depends what your using them for though, colours should be orange (3), white
(9), brown (x10), gold 5% tolerance.
Right bunch of numpty's working in Maplins just lately though.
Cheers,
Bob
[Edited on 14/5/09 by splitrivet]
I used to be a Werewolf but I'm alright nowwoooooooooooooo
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mkblade
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| posted on 14/5/09 at 11:31 PM |
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its to fit in the pink wire that goes to the ecu on the honda fireblade
i.e the voltage should be 9volt going to the ecu on that wire
simon
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iank
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| posted on 15/5/09 at 06:46 AM |
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I expect they gave you what you asked for if you didn't ask for the correct wattage. Probably 1/3 Watt (iirc that's what they used to
sell as standard).
What's it used for on the car, that will tell you what wattage you need, if it's for LED lights then you need a big finned resistor on a
heatsink - but that's not what the red one is.
To test a resistor on a normal multimeter
Switch it to the 2k (or 2000) Ohm switch position usually marked by an omega symbol, make sure the leads are in the right sockets (COM and the one
with the omega) and put the probes on the resistor leads. Should read something around 390 on the screen if it's working (actually anything
between 350 and 430 ish if it's 10% tolerance)
Last time I was in maplins and asked for a single resistor I got odd looks and they gave me two the same - possibly a policy thing.
[Edited on 15/5/09 by iank]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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wilkingj
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| posted on 15/5/09 at 07:29 AM |
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Do you know how much current is running through the resistor?
The biggest problem I see is that of the heat dissipation in the resistor and the wattage of the device.
Check whether it gets warm or HOT.
If its HOT then the resistor is not of the correct power rating (Watts).
I would not wrap the resistor up in the loom, but protect it, or mount it and keep some air around it.
You need a resistor of the correct value (390ohm ?) which you appear to have.
However, is it the correct wattage rating?
That will depend on how much power is being dissipated in the resistor.
As it drops the voltage, it looses power in the resistor, and it gets warm / hot. This is the power being lost in the form of heat.
I would measure the current flowing through the resistor, and then measure the volt drop across the resistor.
The power in the resistor is calculated by P=IxV (Power in Watts = Current in AMPs x Voltage in volts ACROSS the resistor) this figure needs to be
LESS than the rating of the resistor itself. Its not rocket science, when you know how to do this.
If you are dissipating 5watts in a 1/3 watt resistor it will get VERY HOT, and probably burn out, and could cause a FIRE.
If you are dissipating 5Watts in a 5Watt resistor (may need a heatsink) thats Fine its within tolerance. However, if it was on the limit, personally
speaking I would use a higher rated device for that bit of extra safety margin!
If you are dissipating 5Watts in a 10Watt resistor, it probably wont even get warm.
The smaller resistors there are probably 1/4 or 1/3 watt rating.
The larger one could be 1W or possibly 2W.
Have a look at the code on the reciept, then look it up on the maplin site.
The upshot of doing this and getting it wrong could be a fire and serious damage to your car.
PLEASE ensure you have the correctly rated component for the job. I wouldnt want to be reading in a few months about how you are rebuilding a burnt
out shell
I know thats a worst case scenario... But do you want to take the risk with your pride and job for a 50p component?
EDIT
The colours should be:
3 band scheme - Orange White Brown (39 +1 Zero =390) plus gold or perhaps brown 5% or 1% tolerance
4 Band Scheme
Orange White Black Black (3 9 0 + 0 Zeros) plus gold or perhaps brown 5% or 1% tolerance
The wattage will be down to the size of the component, a they are not usually marked with the wattage.
[Edited on 15/5/2009 by wilkingj]
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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02GF74
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| posted on 15/5/09 at 07:33 AM |
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they are f***ing idiots in Maplins. The number of times they have given me the wrong value is not worth mentioning .... but I just did 
Now I always check the colour bands and if in doubt, get them to measure them - on one occasion the maplin monkey wanted to argue since the resistors
came from the tray marked X ohms yet were 10 x out - I ended up going behind the counter and looking for hte correct one.
But back to your problem.
It is hard to see the colour bands but they don't look right.
390 would be orange-white-black-black brown (5 band) or on the larger ones 4 band orange-white-brown-gold
as ^^^, they can be connected either way, the colour of the body is whatever paint the manufacturer decides to use.
take the 2 small ones back and get a bigger one - probably 2 W.
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BenB
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| posted on 15/5/09 at 02:07 PM |
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They look like 0.6W resistors to me.
But if you've got the right reistance what's the problem?
Let's assume you applied 12v straight across it (worst case scenario and not likely to be the case as it won't do anything other than make
heat)
I = V / R
I = 12 / 390
I = 0.03A
W = 0.03 * 12 = 0.37W
So even if you applied 12v across a 0.6W 390 ohm resistor there wouldn't be a problem though it might get hot. But if you've got in
enclosed in a loom you're encapsulating 0.37W whichever way you look at it. Whether it's a 0.6W resistor or a 100W resistors it's
still 0.37W you're trying to loose!!!
I suspect they've given you two resistors to connect in series.
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flak monkey
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| posted on 16/5/09 at 08:27 AM |
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The size difference could be down to two reasons, either they have supplied the wrong power rating resistors, or the original one is old. Newer
resistors are really very small in comparison to old ones of the same power rating. Last time I bought some 1/4W resistors they were the same size as
older 1/8W ones. So its difficult to tell the power rating of new resisitors by simply comparing them to the old ones.
As others have said, just try them with a multimeter. 390ohm isnt a std value IIRC.
David
Sera
http://www.motosera.com
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iank
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| posted on 16/5/09 at 08:43 AM |
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quote:
Originally posted by flak monkey
...390ohm isnt a std value IIRC....
390ohm is standard in E12 and better
http://www.logwell.com/tech/components/resistor_values.html
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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