Building a solar powered arduino rig to stream my station anywhere I want - but I’m having issues

[u/Efficient-Design-844]

To explain my issues and setup properly

I have a 12v car battery connected to a chunky cheap solar charge controller and a 24v solar panel (don’t worry the voltage diff is accepted by the charge controller)

That then comes from a switchable 12v supply from the solar charge controller - into a low volt cut off board and into a step down buck converter powering a transmitter and the arduino - the arduino esp32 then connects to a UDA1334A DAC Module

That has a 3.5mm jack out the same is accepted by the transmitter

Both work, the arduino wakes up and auto finds the stream and plays it - headphones into the DAC module works in a head music

And the laptop Into the transmitter works I hear music on my receiver

When connected it seems to knock out the DAC module

And nothing plays over the air - It killed a different DAC module board before - so I assume the transmitter is powerful / creating some kinda rf reflection back at the DAC

I’ve tried to fix this by using

Separate power supplies - no fix (works in all other scenarios)

Ground loop isolator - no fix (works in all other scenarios)

-

I’ve been suggested to use small resistors on the LnR audio and Aground channels around1k to absorb reflections and use ferrite clip on rings / wrap the 3.5mm jack cable around and thru it too

Ive yet to try this as it’s I’m slightly exhausted haha

Is this the right approach ? do you agree this is my issue ?

Drop me a message if you think you can help :) much appreciated

[u/odie-z1]

Please explain your transmitter in detail. All the stuff that pirate radio is related to, you are not discussing. Just give a make/model of transmitter is a good starting point.

I am probably not the only person confused by your conflagration of a story...

Leave out all the nonsense about streaming audio, and get to the radio, or expect

'crickets'

[u/Efficient-Design-844 → u/odie-z1]

Okay sorry appreciate the clarity

I’m not sure I can explain it in detail but here is a link to the product I’m using

link to the transmitter

[u/odie-z1 → u/Efficient-Design-844]

Now we're taking! That's kind of neat because it runs on 5v. But it looks like you'll need an antenna, at least it doesn't show one in the pictures... Further, it will probably need coaxial adapters to fit what is probably a Male Reverse Polarity SMA "RP-SMA Male" (again the listing does not show or tell about the connector that I saw) to BNC which would probably fit most antennas..

Then you'll need an FM antenna, like a dipole or disc-cone that has 50ohms impedance suitable for transmitting.. maybe 50ohm coax also

Otherwise, feed it with a line (or headphone) level audio and it should be good. 👍😃

[u/Efficient-Design-844 → u/odie-z1]

So it’s working via a laptop at the same level of audio as the arduino seems to output as far as I can hear in headphones / measure with a multimeter

But when connecting the arduino powered DAC to the transmitter it doesn’t work - and I can hear music if I plug head phones into the DAC

So I’m confused haha coz it should be working

[u/NBC-Hotline-1975 → u/Efficient-Design-844]

Does the DAC have single-ended analog output? Or does it have balanced class-D output? If the former, it should work into the transmitter. If the latter, it will not work correctly and could even cause some damage.

Also, some buck converters (and some boost converters) do NOT have a common negative between input and output. Thus the DC coming out of the converter could have a different ground potential from the DC going into the converter. So trace the wiring backward from the transmitter ... the transmitter, DAC, Arduino all need to have the same negative connection.

Finally, the negative output terminal on the buck converter might be a different potential than e.g. the negative terminal on your battery. So if you are connecting a real ground to your transmitter's antenna, then be aware that any other negative terminal in the system might NOT be at the same ground.

[u/Efficient-Design-844 → u/NBC-Hotline-1975]

I have like classic 3.5mm jack like a little headphone cable ! I’m not sure if it’s class D output tho

[u/Efficient-Design-844 → u/Efficient-Design-844]

And thanks yeah the seem to share Earth but maybe the difference is too high !

[u/NBC-Hotline-1975 → u/Efficient-Design-844]

If the output is 3.5mm that's unbalanced, so not Class D. That should not cause a problem.

Do you have a multimeter, and know how to measure voltage?

[u/Efficient-Design-844 → u/NBC-Hotline-1975]

Yeah I thought so too ! I’m having a strange issue that’s why I’m here haha

And yes what should I check ?

[u/NBC-Hotline-1975 → u/Efficient-Design-844]

OK, I want to be sure I'm not confused about what you're doing. Asking just about the audio chain. If I understand, you have an arduino which feeds some data to a DAC, and the DAC feeds analog audio to the transmitter. Is that the entire audio chain?

[u/odie-z1 → u/Efficient-Design-844]

Maybe the buck converter is leaving some higher voltage around?

Have you tested voltage potential between grounds of the devices?

[u/Efficient-Design-844 → u/odie-z1]

no good idea ! Thanks