Power injection

I have a few runs of addressable tape, the furthest one away is getting a bit of bolt drop so needs a power injection.
Does the injection psu have to be the same wattage as the first psu? As in, the first one is a 12v 75w and I have a 30w one to use for the power injection further down the line, will the strip jusy share the power or will it try and draw to much from the smaller psu.

You don’t need multiple supplies, but if you do that, you need to have common grounds (0V) and keep the positives isolated from each other.

I only added another as at the end of the first run of strip I was only getting 10.1vdc so added another psu to bump it back up to 12 at the end of the strip so the next run still had 12volts.

I have a common ground through the strip connections at either end.
Don’t need to seperate the positive so the second psu only powers the second run of strip? Or can they just be connected on the same positive line so all the strips share both psu’s?

You don’t really need a second power supply and is a waste of money unless it can’t provide enough amps for the setup. You just need to run power wires from 1 power supply to both ends of the strip.

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Only fitted due to volt drop, the strips are in about 10 different places all different lengths,
Basically the kitchen cabinets top, worktop and kick boards so not really possible to wire both ends of all the strips.
The extra psu helped loads, strips furthest away where the extra psu is are now work properly at full brightness’

And it seems you missed the part about not connecting the positives.

Injection is usually just done via more wires, not more supplies.


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But just longer wires would not fix the power drop issue?

Yes, it will because you’re running a set of wires directly from the original ps to the injection point. They’re saying you don’t need a 2nd ps.

So she can run another set of wires (positive and negative) to the end of the run and splice them into positive and negative? Can she also use a T connector in the middle? Would that require somehow severing the positive from the 1st half of lights and connecting just the positive or positive and negative?

Solved power drop by putting bigger OS and running cables as guys have mentioned above.
Only issue I have now is trying to set up a max rs-485 in transmitter and receiver modes, any one have a wiring diagram? Can’t figure out the pull high and low of the DE Aand RE pins

The RE line is always “mislabelled”, it should be ~RE - read as “NOT RE”.
That means the RE (Receiver enable) line is active when Low (not High).

The idea is to tie the 2 pins (RE & DE) together, then apply Hi to make the board a Tx or Lo to make an Rx.

Personally I like these RS485 boards:

Auto switch RS485

They’ll auto configure themselves for RX or TX depending on how you hook them up.
Plus they have a good batch of power protection circuitry built in.

Bigger PS? What did you go with?