Output impedance, what is that exactly? In the simplest case, it is a reasonable way to explain the maximum amount of current a particular power supply can provide. Power supplies, including batteries, can be modeled as having an “internal resistance.” The value of this internal resistance is the same as the “output impedance.” Then, the circuit as a whole can be studied using the resistance and voltage laws of voltage drop based off of resistance. A higher output impedance (resistance) value means that the output voltage will more readily sag when there is a high current draw (low resistance) load attached. Conversely, if a low current draw (high resistance) load is attached, the voltage drop will be negligible even if there is a high output impedance.
Therefore, the output impedance is primarily a measure of how much current can be supplied by a power supply. Low current, i.e. high resistance, outputs can alwyas be connected without issues, but high current, i.e. low resistance, outputs need to be connected with care. Motors are characteristic for causing high current draws and voltage sags in power supply sources. You may need to consider switching to a power supply with a higher current rating, i.e. lower output impedance, if your load’s current draw is too high, i.e. resistance too low.
20191116/https://en.wikipedia.org/wiki/Output_impedance
So, the whole characteristic impedance thing, I still don’t quite understand, maybe it is better explained in the transmission line article? Well, not really. Basically, the key point to understand about characteristic impedance is this. Complex impedance is defined on alternating currents, and it cannot be understood as being identical to simple impedance on direct current circuits.
But, the transmission line article does have some useful mention of various types of wire for high-frequency transmission, with “microstrip” being an interesting variant for signal transmission on a printed circuit board.
20191116/https://en.wikipedia.org/wiki/Transmission_line
Here we go! This article explains reflections very well.
20191124/https://en.wikipedia.org/wiki/Reflections_on_copper_lines
Okay, but it doesn’t quite explain enough on how to build your own “bus-style” line, so it seems. How would you build in side-taps that result in minimal signal reflection? Well, thinking this through intuitively and thinking about some ways in which it was done successfully in the past, I’ll pitch in my guess. With side taps, you want to hvae minimal surface area of the side wire tap in contact with the bus wires. This will ensure that the current flowing out of the wire is approximately the same as the current flowing in. If you had a side tap the same size as the bus wire, there would be a lower resistance on the two outgoing branches combined than the incoming branch, since there would be twice the wire cross-section, and that would cause an impedance mismatch that you could get a signal reflection off of. So, your connections to the bus wire must be high-impedance, and the ends of your bus wire are terminated with the same impedance as its characteristic impedance. This is fairly consistent with old-fashioned “vampire-tap” style Ethernet wiring, for example.
Well, let’s keep searching.
20191124/https://en.wikipedia.org/wiki/Bus_network
Oh, yes the hint is “T connector.” Sometimes also called “tap connector.” Let’s go searching on those lines.
20191124/DuckDuckGo rs-485 t connector
Ah, yes, here I find more useful information on how to do RS-485 wiring. The head-end of a bus should be wired to a transceiver, and only the opposite tail-end should be terminated with a resistor. As for the T connector design themselves, that I need more information on.
20191124/https://www.se.com/ww/en/product/TCSCTN011M11F/network-%e2%80%9ct%e2%80%9d-connector—rs485-network-or-canopen—m12—5-pin-1-male–2-female
20191124/https://eeci.com/rs-485.pdf
how to do rs-485 t connector
http://www.bb-elec.com/Learning-Center/All-White-Papers/Serial/RS-485-Connections-FAQ/faq_rs485_connections.pdf
https://blog.opto22.com/optoblog/rs-485-to-terminate-bias-or-both
Okay, okay, I think I’ve searched enough. Looks like there actually isn’t too much formality in the T connections of RS-485 wires, for instance. It is rather primitive, just find a way to make a connection, no need to worry about different wire sizes affecting overall impedance, and that works good enough. Speeds less than 19.2 kbits/sec on cables less than 4000 feet will have no issues.