I’m planning to add a momentary switch to a single loop DC circuit. Will this cause any amount of resistance in the circuit? I’m a complete noobie when it comes to electronics, any resource links or clarification is appreciated. I know the type of material/width of wire and a pot will cause resistance but will any component put in line with the circuit cause resistance, and if so how do I go about measuring the resistance for each component within the circuit?
Every material has resistance.
You can calculate a materials resistance using its resistivity and dimensions. For a simple wire, the formula is R = p*l/A, where p is resistivity, l is length, and A is area (cross sectional. Imagine cutting the wire, you’d see a circular cross section).
Some materials like copper have very low resistance.
Some materials like oil have a very high resistance.
Some materials like carbon have a resistance somewhere in between, but generally fairly high.
Resistors use a strip of carbon to make a high resistance path.
Resistance in a switch is typically minimized by design, so introducing a switch or button should not introduce a lot of resistance. It is tyically better not to use switches of this type in signal critical or high power applications (e.g. sound or battery charging), but charging up a small capacitor or powering a small dc circuit should be fine
To measure resistance, one can use a multimeter. This makes use of Ohm’s law. Ohms law shows that
V=I*R
Where V is voltage, R is resistance, and I is current. When a small voltage is applied across your component, the current is measured. Then using the current and voltage, it can figure out what the resistance is. It shows it to you on a display so all you have to do is touch the probe tips to the two legs of the switch.
For a switch this will typically be less than 1 ohm. If you buy from a reputable distributor (e.g. digikey, mouser, arrow, farnell, even LCSC) you can get the “datasheet” and look for the constact resistance. This might be a bit harder with ebay/amazon/aliexpress parts, so just stick with a multimeter.
A cheap handheld one is fine, but I’d say prob look for an EEVBlog or other video looking at good cheap meters; you can get pretty good stuff without breaking the bank. Don’t stress over it though; any multimeter is better than no multimeter
Awesomesauce! This is exactly the clarification I needed as I unfortunately got my part from a less “reputable”, that being Temu, source.
What are you switching? There’sa good chance (but no guarantee) even an ultra-cheap switch is fine.
A 12 volt battery w/ a pot and a few other components. The plan is it wont be running more than 5 milliamps through it. I ended up getting this so not exactly a conventional momentary switch.
That is pretty much exactly a conventional momentary switch. It just happens to be packaged for use controlling something a little different.
It should be fine for your application.
One thing to note - the contacts will probably “bounce” as the switch is closed. Produce a string of momentary connections and disconnections for, oh, say the first few thousandths of a second. That’s perfectly normal for a mechanical switch.
That won’t matter in its intended application. But if you are using it with electronics, say counting the number of times the switch is operated - the results can be unexpected.
You can look up “debounce” to see how this can be worked-around.
Thanks, I appreciate the clarification on the switch just having a different housing. I’ll have to do some further research on “bouncing”, interesting stuff.
Unless you’ve managed to get a switch made out of superconducting material and you’re working inside a liquid helium bath, everything has resistance :)
You’ll have a bad time trying to measure such low resistances, so usually you can look at the datasheet for the switch you’re using or for a similar switch if you need a ballpark number. You’ll see an on-resistance, and a max current (since there will be arcing when you open the switch).
If you do want to measure the low resistance, you’ll need dedicated meter with a kelvin connection.
If you do want to measure the low resistance, you’ll need dedicated meter with a kelvin connection.
You can pass a known current through the switch, measure the voltage drop with a multimeter and use ohms law to calculate the resistance.
Thanks for the feedback and info, I’ll know what to look for next time. Unfortunately, I purchased a tattoo pedal as the momentary switch, thinking it would be easier to operate. link Btw. thanks for clarifying everything has resistance, that concept confused me more than I thought it would.
Open it up!
They put a regular old switch inside a fancy box, but you’ll be able to read the part number once you see the actual switch.
I’ll give it a go, fingers crossed.
Some resistance? Yes.
Significant resistance? No.
Realistically, you need to put together a circuit and measure it with a Multimeter.
