I have a project where i give inputs to an Ikea Fyrtur shade/cover from an arduino. The project itself works as expected, i can send out the instructions over uart to the Fyrtur PCB and all actions are executed properly by the cover.
As this will be part of home automation, i also added a connection between the arduino and KNX (home automation protocol). This entire stack works as expected; I can send knx commands and the cover responds.
As a second phase of the project, I would like to get rid of the battery power used by the cover. Since the knx bus already provides a 30V output, I thought of using a DCDC converter (LM2596) to power the cover. When i use the cover with the DCDC converter without any arduino connected everything works, it provides sufficient power and the cover operates normally.
However when i combine these two approaches this does not work (see schematic below). The commands are not received by the arduino. Could it be this DC-DC converter introduces noise in the serial communication? How could this be resolved?
Motors have a high startup current so it's possible that the DC-DC converter isn't able to maintain the voltage during the first few milliseconds of the motor startup.
Try adding some big capacitors between the 7.5v and GND.
I would give my vote to power issue like mikb55 wrote. But yes, dcdc converter can disturb serial, keep your serial wires short as possible and far away from power wires.
You mention that it works fine with the DCDC when the Arduino is not connected, implying you are running the blind with the Ikea remote and then it works fine.
When you add the Arduino, does the Ikea remote stop working as well, or is it just the Arduino control that doesn't work?
It could be the DCDC ripple, but it seems unlikely it would cause a communication problem with the Arduino if the Fyrtur is working properly in all other aspects.
What's the actual battery voltage when connected to the Fyrtur? Where did you connect the DCDC on the Fyrtur?
One thing to check up is the UART voltages and make sure the Fyrtur really works with the levels from the Arduino. If there's a difference in the DCDC and battery voltages that might have an impact.
I did indeed try the DCDC without the arduino. For this i didn't use the remote, but the buttons on the shade itself (which work).
When i connect the arduino with the DCDC, the shade does not work anymore (it doesn't react to the button presses anymore).
I didn't think power was going to be the issue, because the rx/tx and the software serial ports were all put to 3.3V. Another thing i noticed is that i just cannot communicate to the arduino; it doesn't respond to a regular "health check" without any interaction with the shade, so the hardware RX/TX doesn't work anymore either.
The battery voltage was meased at the battery connector side and is 7.8V, which i've put the DCDC converter as well
This was eventually fixed by using the XL6009 module, another DC-DC converter producing much less noise compared to the first one i used. Now I've got this working with the DCDC converter and uart communication.
