hi, sorry if this is in the wrong section, i am attempting This: http://www.kpsec.freeuk.com/images/sigcd.gif circuit, and in my local electronics shop (maplins) they dont have the 1k resistors required (2 of them needed) so, what would be the conciquences if i used two 1.5k resistors? would there just be a longer gap for the light to come on?
I am using this circuit for a model railway signal.
Thanks in advance, Mike

 

Looking at it, they are current limiting resistors for the LEDs, the implication would be that the LEDs appear dimmer with 1.5k than with 1k. The circuit should still work fine though. 1k is a pretty common value anyhow, its worth getting some when they re-stock.

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Angry!? I'm absolutely electrolytic!

Will have to make do with myspace now I guess...

 

You may use 910 or 820ohm resistors. LED's will shine stronger than with 1.5k.

 

While the value is important the 1k can vary somewhat as must be obvious from the previous posts. No reason you can't take two 470 ohm resistors and put them in series - or parallel a number of higher values to get close. This can work for DC and relatively low frequency applications as long as space isn't an issue. When I've been breadboarding something I've actually used pots and adjusted them with an ohmeter. Keep in mind that small pots can't really handle much current.

Don't forget to consider heat/power. You've got 12 volts supply and you might see that across the LED/resistor combination - with 10 volts being dropped across the resistor - 10 volts and 20 ma is 0.2 watts - so it's more than an 1/8 watt resistor can take - ok for 1/4 watt. Nothing precise about what I just did but you get the idea.

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stevez

 

thanks for the replies,
if i use 480 oms, wont the LED's blow quicker? or wouldnt there be much difference? Dr.Em, the 1k resistors are discontinued, not out of stock
Thanks again, Mike

 

1K resistors are an EXTREMELY common value, if they are 'discontinued' at Maplin it's because they are stopping selling components all together!.

It's like going to your supermarket and being told that "tins of bean have been discontinued"!.

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they sell all other components, diferent value resistors, capacitors, IC's ect.
Verry strange :?

 

hi again, for the circuit, i need a "relay SPCO 12V coil" would the "12V/12A Min Relay" here: http://www.maplin.co.uk/Module.aspx?...=2512&doy=2m10 be sutable?
Thanks, Mike

 

Depends what you are trying to do with it?, your specification isn't complete enough.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

oh sorry, thaught i posted a circuit diagram, i am planning to make this: http://www.kpsec.freeuk.com/projects/signal.htm

 

could i use one of these: http://www.mutr.co.uk/prodDetail.aspx?prodID=298 ??

 

I find it hard to believe that Maplin don't sell them. I imagine you probably asked an assistant...? Maplin used to employ people who knew their stuff, or at least had a basic knowledge of electronics. Now it seems if you don't have the part code at hand, they can't be bothered to help you. Last week I went to buy a 240 - 12V transformer. The guy didn't really have a clue what I was talking about, and he was supposed to be the component guy. He just said "we probably don't stock them" and that was it!... Maplin are not in my good books. Their prices seem to be creeping up as well. If they don't sell them seperately, they will at least sell them in a pack with other values. But I think your best bet is to get on Ebay (if you are old enough?) and have a look around. I think there's a guy who sells packs of 100 for 35p! Or you could get a pack of say E12 series off Ebay for quite a bit less than Maplin.

Cheers,

Mike

 

thanks, Last time i went to maplin i had no problems (probably because i looked on there site and wrote down the order codes!!!) i also asked them about a soldering iron tip for my old Weller soldering iron. he had a look and said they didnt stock them and told me that i might be able to get one from the weller site... i just baught a new iron lol...
I was told by someone on the DAL comp. help forum that you have to be 18 to use e-bay but my mum created me an account in her name, and when i got my card i just added that to pay pal and deleted my mums (she doesnt use it).. i will have a look now, thanks alot

Mike

 

i found this: http://cgi.ebay.co.uk/RELAY-MINIATUR...QQcmdZViewItem but i dont want to spend £8.50 on 10 and only use 2 (which is how much i need) might look around on other sites. could i use a 3A relay: http://www.maplin.co.uk/Module.aspx?...ges&doy=search ?? here is the datasheet (pdf) :http://www.maplin.co.uk/Media/product_pdfs/yx94.pdf

Thanks, Mike

 

I have some 5V relays you can have for £1 each... (RRP from R.S. £4.41) I'm not trying to make money - I got them at the same price. I live in East Yorkshire so p&p should be 30p. Let me know if you're interested (you might have to adapt your circuit slightly - a resistor in series would do it methinks...)

Cheers,

Mike