Arduino starter kit and course bundle


#1

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#2

This looks like a really nice kit, but

•1 1M resistor

That’s a really big resistor.


#3

I am personally shocked by the lack of any zero Ohm resistors…

Still, this looks like a nice kit for 85 bucks.


#4

They are there. They look like the patch wires. :stuck_out_tongue:

In the land of CMOS logic, not so. The input impedance of the FETs is staggeringly high. (So, avoid dangling inputs. They tend to get all sorts of signals coupled to them, and then oscillate, or settle in undefined states with the transistors half-open, and take current they don’t need and may cause heisenbugs. If you can, pull-up or pull-down them.)

Also, even in the land of analog tech. You’ll often see them in the op-amp circuitry. I recently used a 1-meg:1-kilo divider to pull up an op-amp input for a current sensor just a little, to get it to linear part of the characteristics (LM358 is not really a rail-to-rail and at few millivolts against the minus power (ground, here) they register zero). The ADC complained that it got about a dozen bits above zero, but that was handled in software.

Then there is the land of high voltages. The measurement circuitry involves resistor dividers that quite often can run in tens to hundreds of megaohms, and can be quite expensive. See an example of homemade 100-meg resistors here:


(Yes, I know, I am voltage-overloading the 10meg SMD ones a little.)

With such high resistances, however, cleanliness is of high importance. Minuscule traces of flux or other dirt on the board can and will attract moisture and lead to leakages, which behave like high-value (sometimes not-so-high, too) resistors of time- and environment-varying parameters. (Quick test: breathe at the board. If the added humidity swings the parameters, you have a dirt-related leakage issue.) Tracing these bugs is quite annoying; so if you can, stay within the 100 kiloohms range if you are a very beginner, these problems then can be usually neglected there. (Similar with stray capacitances and high frequencies, they get more than annoying! Everything gets annoying at high freqs!)


#5

Aha, megohms! I thought capital M was meters. o.o;;


#6

You can have these too :smiley: Just use a resistive wire. Or, for flexible heating applications, you can use the 316L steel, available as threads or raw yarn from Sparkfun. With about 4 ohms/meter for one of them, give or take as I remember, attaching it to a USB charger power bank will give you about 6 watts of warmth, sewable as you want. (More about the material later, it’s in the mail.)


#7

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