I’m just checking that the variable resistor symbols arrow doesn’t have a correct orientation.
For instance, is there a convention that says the arrow has to point in the direction of current or does anything go? 
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Before being concerned about orientation, you need to decide whether your variable resistor is a rheostat or a potentiometer 
I don’t think that the formal standard specifies an orientation, although standards such as IEC are kept firmly behind a paywall and you can only go by commentary and examples. In practice different types of components would be subject to different norms. For instance your transistor looks odd to me when rotated 90 degrees, but horizontal flipping is common, while vertical flipping much less so. For a resistor or potentiometer any orientation looks OK. For an LED or LDR the little arrows have some real-world meaning that is worth paying attention to, and so on.
Since the purpose of the schematic is to communicate the operation of the circuit the determining rules should be things like clarity and consistency. But in some cases an unusual orientation might enable a much clearer layout to be drawn - that’s often the case where there are multiple identical segments to the circuit.
Of course, when the symbols are used for other purposes then other rules apply - for instance symbols placed on a PCB must be oriented to the actual component placement.
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Ok, good rule of thumb
Ah I didn’t know that. I’m sure PCB design is coming for me… very soon. 
I’m hoping this choice will be justified in context.
I’ll link to it when I am done and I’m sure people will let me know if I made the wrong choice 
Ah! This tells me I still don’t understand the language around this ‘Resistor Dial Thingy™’ 
I thought:
A potentiometer : is the name for the physical electronic component that has a semi-circular restive strip and a moving contact that rotates across the strip.
A rheostat : is a big tube thingy which can be mimicked by a potentiometer by connecting wires to the center and a single outside pin.
When I communicating that I want a pot to be wired like a rheostat I use this B from the picture below.
So I thought that it was possible for a potentiometer to be a rheostat at the same time, since one the name of the physical dial and other a configuration of that dial (in this context).
I have a mistaken belief?
Where did I go wrong?
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The terms are often used loosely, but typically ‘variable resistor’ is the generic term while ‘rheostat’ and ‘potentiometer’ are more specific. The rheostat is distinguished because it only has two terminals, but also because its usage is different - you can use a potentiometer like a rheostat, but it is not suitable for the likely purpose. There are other types of variable resistors, like LDR, thermistor and varistor.
The IEC symbol dictionary distinguishes between rheostat and potentiometer, and you will also sometimes see trimpot as a different symbol (your third example) even though it has three terminals.
You will also sometimes see IEC and ANSI symbols mixed in one diagram, which suggests a cut-and-paste design!
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Yeah ok. Just some jargon norms I’ll get used to eventually
Ah, What’s an example of a moment where a rheostat would be used, but a potentiometer is not a suitable substitute?
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A rheostat is used to control current - a potentiometer controls voltage. A controlled current is likely too high for a potentiometer to handle - the typical power rating for a potentiometer is a few Watts at most, whereas a rheostat is unlikely to be rated at less than 5W and probably much more.
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Gotcha.
In this case I’m dealing with super small wattage.
My variable resistor is standing in for Rb in an Astable 555 and I’m only rocking 5v.
I’m choosing to think of this pot as varying the ohms so I’m happy with the generic variable resistor symbol for the purposes of this schematic.
This has been a nice “inside baseball” on how experienced people read schematics and what the different symbols imply.
Learning all the time.
Appreciate you @Jeff105671.
Pix 
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The symbol should match what you are actually using (a potentiometer with one end and the slider connected). Using the rheostat symbol for what is actually a potentiometer (even though that is the function you intend) would be confusing because it implies that the connection is to each end of the track and the wiper is not connected.
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Hi Jeff
Butting in here but
Yes it does. Normally if this is the case the base is pointing down. This is normal in a “Common base” configuration where the base is grounded (“common”) sometimes via a resistor and the signal input is to the emitter. this is just one of 3 possibilities. The other more common ones are common emitter (an inverting amplifier) and common collector (emitter follower).
Yes they signify an optical device. The orientation (pos and neg) are dictated by the diode symbol. A resistor is not normally polarity conscious.
Cheers Bob
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Yes - that shows the correct function as well as the actual component.
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I’ve noticed KiCad has a different option for TrimPot and Potentiometer.
I had to use a trimpot, because that’s all I could source in 20k, but I would prefer someone to use a quality potentiometer.
Should I mark what I had to do due to my limitations (trim) or what I would have liked to have done if the products were available to me (quality pot)?
Hi pix
Altronics, Element 14, RS Components, strange Jaycar don’t seem to stock that value but the do stock a 25k linear RP3514.
Cheers Bob
That decision is based on the intended audience. If you are documenting it ‘as built’ then the symbol should be the actual component you used. Otherwise when you come to look at it some time in the future you will spend time puzzling over the discrepancy. If you intend if for others then the symbol needs to match the parts list - a 20k trim pot if that’s the best available option, or the actual recommended value rotary pot if that’s the way it should be built.
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Hi Pix, Jeff
A comment about using a rheostat or a potentiometer connected as a rheostat, that is current control.
These devices have a wattage rating, 1W, 5w, etc. That is over the WHOLE of the resistive element be it carbon or wire
Say you have a rheostat rated at 10W, resistance 5Ω, applied voltage 5V.
The formula for power is E^2 / R, That will be E^2 = 25 so 25/5 = 5W, all good so far.
Now we set the rheostat half way at 2.5Ω, the applied voltage is still 5V.
It would be fair to say that the half of the resistive element would be capable of dissipating half the rated power which would be 5W.
Now we have E^2 / 2.5 = 25 / 2.5 = 10W but the half resistance is only capable of handling 5W.
So we now have a very hot resistor which is probably going to fail.
This is where you can come unstuck using say a 500mW potentiometer, particularly the carbon types. If you have this across a supply and are approaching even half the dissipation limit over the whole element and you get down to low resistance it does not take long to greatly exceed the capability and ultimately destroy the device.
With the hypothetical situation above using a large (10W) resistive element there will be some heat dissipation in the unused section but for theoretical considerations you could ignore this as it would not alter things much.
There are a few more things to think about besides the resistance.
Cheers Bob
Ah matching the parts list really resonates with me.
I think I want to use the trim pot symbol then.
I think I should also leave a note saying that “potentiometers are preferred over trimpots if available”. Is there a convention for notes in a schematic?
I’m asking a lot of questions about schematic layouts and I really appreciate your help as always.
I can’t be the first hobbyist maker to have questions about how to do this.
How do casuals like me learn about this stuff?
Hi Pix
By making mistakes. Then learning from them.
Cheers Bob
Ah that’ll be easy for me! Mistakes are my specialty.
Hehe… I was going to say nothing… but you can always learn from others mistakes… ie. copy, then wait for someone that knows to say “that’s not right” …
My personal view is we dont have enough (young) people getting into this stuff and we need the new generation to be the inverters of the future. So anything that can help everyone learn the standards should be open and available.
… but I dont make the rules…
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Hi Michael
What standards. There seem to be a plethora of “standards” these days. This has been going on for some time and some of it is good. A classic example is the consortium of Sony and Phillips who got sick of waiting for the “standards” committee or whatever they called themselves to come up with a “standard” system of digital audio transportation so we finish up with “SPDIF” (Sony Phillips Digital InterFace) which was not a bad thing, at least somebody did something. This has become some sort of “standard” system over time.
Fortunately some standards still survive as in the case in question regarding electronic symbols although there are 2 in general use.
Cheers Bob
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