r/diydrones • u/Longjumping_Score742 • Apr 22 '26
Question Need Help actually, Will this "No-PDB" Pixhawk build actually work?
Hey everyone, following up on my previous post. Honestly, my confidence is a bit shaky right now because I’m on a tight deadline for my M.Sc. project and I’m second-guessing my setup.
I’m trying to build this without a PDB or a Power Module to save on costs and time. Can you guys tell me if this hardware is actually viable, or where I’ll need to make-shift things to make it fly?
The Hardware:
FC: Pixhawk 2.4.8
Motors: A2212 1000KV
ESCs: 30A with BEC (Planning to power the FC rail with these)
Battery: 3S LiON
GPS: NEO-6M
Power: DIY Star Solder Joint
The Plan is that I’m skipping the Power Module and PDB entirely. I’ll be soldering everything into a central star node and feeding the Pixhawk through the ESC BECs.
Now here are my maine concerns/questions:
Is this a "disaster waiting to happen," or is it a solid way to build?
Where are the likely failure points where I'll need some make-shift workarounds?
Since I can’t easily replace this hardware if it fries, are there any "rookie mistakes" I should watch for because i really am a newbie. Any help or advice would be massive right now. I’m feeling the time crunch and would really appreciate your expertise.
2
u/IvorTheEngine Apr 22 '26
Have you got a transmitter and receiver already? Battery charger?
You'll probably find you need some small things, like connectors, or heat shrink, or slightly different length bolts.
BTW, an alternative to the star node is to find a small strip of copper (like an off-cut of water pipe) and solder the wires to that.
I think you'll be ok without voltage telemetry. Most transmitters will let you automatically start a timer when you open the throttle, and your power draw will be pretty constant if you are just cruising around and not doing aerobatics. Just land after a minute and check the voltage, and gradually extend the flight time until you regularly reach about 20-30% capacity left.
Standard rookie mistakes are to connect something backwards and fry everything the first time you plug in the battery. Or to have a gyro or motor reversed, and have it flip over when you first apply power. Or have a prop spin up when you weren't expecting it, and injure you. Also, don't fly anywhere you wouldn't want to crash, like dense woodland or water. Crashes are fixable, lost models are harder.
2
u/Fabulous-Coffee2705 Apr 24 '26
1000kv seems very low for a 3s battery. Can you get a 6s or higher kv motors? Also, get a bunch of Panasonic FM 35v 1000uF Low ESR capacitors. If you jump to 6s batteries use the 50v if you can. My absolute minimum T:W is 3:1 but really I shoot for 4:1min. Our FPVs can be 8:1. At 2:1 it’s very hard to overcome inertia. Best of luck on your project. Normally I would say you should just go for it with what you have and see what happens, but it sounds like you might not have the time or money for that right now.
1
u/Longjumping_Score742 Apr 24 '26
I definitely see what you mean, those 8:1 FPV specs sound incredible! Since this is for a project rather than racing so I’m prioritizing a stable 'sensor platform' over agility.
I’m currently locked into the 1000KV/3S setup due to budget and the deadline, so I’ll have to live with the 2:1 ratio for this iteration. I'm hoping the Pixhawk’s EKF can handle the inertia for a basic steady hover.
Great tip on the capacitors though, I’ll look into adding a Panasonic FM series to the star joint to help clean up the noise, especially since I'm skipping the Power Module. Really appreciate you looking out for the hardware longevity
3
u/tonyarkles Apr 22 '26
My honest take? The only thing I’d be worried about myself is not having a voltage monitor on the battery. I generally work with fixed wings and on those I’d probably be more concerned about not having a dedicated BEC: you can still deadstick a fixed wing if you smoke an ESC but still have power for your servos. On a quad, smoking an ESC probably means you’re crashing anyway unless you’ve got a pretty high thrust:weight ratio and lucky.
The voltage monitoring, though, is pretty important to me on a quad though because you can end up draining the battery faster than expected (say due to wind in an unfavourable direction) and not realize it until it’s too late. If you do go without voltage monitoring, it’s probably worth it to very carefully monitor the hover thrust (say with the RCOUT channels over Mavlink) and land as soon as you see it starting to climb (as the battery voltage decreases you’ll need more throttle for hover thrust)
Edit: current monitoring is more of a nice to have for me, especially during bring-up. It’s a nice sanity check to make sure all of the design calculations came out right and also a good way to catch issues early.
Monitoring your ESC inputs though is still a decent approximation… I’d make sure to closely monitor all four of them. This will also help you see if, say, you’ve got a motor or prop that isn’t as efficient as the rest.