What does the R in resistor value 240R mean? - diyAudio
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Old 16th April 2005, 08:43 PM   #1
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Question What does the R in resistor value 240R mean?

I'm a newbie in the world of DIY electronics, and was wondering where I can get info on what the R means in 240R resistor on a schematic. I know it's probably a simple question, but I am a beginner.
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Old 16th April 2005, 08:46 PM   #2
jleaman is offline jleaman  Belgium
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240R means 240 Ohm : O )
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Old 16th April 2005, 08:53 PM   #3
Zombie is offline Zombie  Sweden
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1R8 = 1,8 ohm
10R = 10 ohm
1k2 = 1,2 kohm
12k = 12 kohm
1M = 1 Mohm

Get it?
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Old 20th April 2005, 10:50 PM   #4
cpemma is offline cpemma  United Kingdom
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The 'letter marker for decimal point' system was introduced to reduce reading errors on schematics; with resistors using 'R' also means you don't have to remember how the heck to get the ohm symbol ( Ω ) - more info here (pdf).
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Old 20th April 2005, 11:17 PM   #5
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R means resistance and is used instead of the decimal point.
The decimal point is sometimes hard to see.
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Old 21st April 2005, 12:35 AM   #6
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to complicate things here's the info I got on caps ratings:

QUICK REFERENCE CHART (Decade values)
1R0 = 1pF 103 = .01uF
100 = 10pF 104 = .1uF
101 = 100pF 105 = 1uF
102 =.001uF 106 = 10uF
1010= Some numbers used on 10 meters!

I saw that in datasheets too (though you very rarely come across caps smaller than 10pF, so the "R" is hardly ever seen on capacitors anyway)

Just to say that "R" probably means something else than resistance in that code...
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Old 21st April 2005, 02:16 PM   #7
cpemma is offline cpemma  United Kingdom
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Quote:
Originally posted by Dominique
to complicate things here's the info I got on caps ratings:

QUICK REFERENCE CHART (Decade values)
1R0 = 1pF 103 = .01uF
100 = 10pF 104 = .1uF
101 = 100pF 105 = 1uF
102 =.001uF 106 = 10uF
Those numbers are usually seen marked on the part rather than in a schematic, especially on small caps. A bit like resistors, the first two give the value, the third the multiplier (number of zeroes), result in picofarads, so 472 = 4,700pf = 4.7nF; schematic may show 4n7.
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Old 22nd April 2005, 08:21 PM   #8
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Cool! Thanks for the info, guys!

What if the schematic reads just 12 for the capacitor (like C1 in the attached schematic)?? I'm having a problem getting it to work. Either my inputs are wrong, my outputs are wrong, or the schematic itself is wrong. I'm assuming the - V coming from R4 is the positive voltage. Would it need more than 9volts (I started low, and worked my way up to 9 volts)
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Old 22nd April 2005, 08:59 PM   #9
Byrd is offline Byrd  South Africa
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I would imagine it means uF or microfarads in this instance. The capacitors shown are polarised. IE there is a + and - pin. The - pin is usualy marked on the capacitor with a big black stripe on the casing.

Voltage looks to be NEGATIVE voltage

Is the circuit correct? - Sorry not qualified to answer that one for ya
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Old 22nd April 2005, 09:11 PM   #10
kevinkr is offline kevinkr  United States
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This circuit is a common emitter amplifier using a pnp transistor, and the voltage on the collector of a pnp is negative relative to the emitter.
Connect the negative side of your 9V battery to V- and the positive side of the battery to the circuit ground. The circuit as drawn is fine, and you can use 10uF electrolytics in place of the existing 12 (uF) caps shown.

Kevin

Edited to add additional comment.
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