uhhhh…Why? there is no feedback. It’s just 5v power supply. Whether the second side of the splitter is cut or not, The vescs have no idea. The only issue is some receivers can trip out on inconsistent voltage. Thinking you have to use canbus is in line with thinking you have to use 2 vescs…lots of damaged single motor builds due to this confusion right?
Actually yes there is, if you have one vesc at 5.00V and the other at 5.1V connected in //. You have a 0.1V that is creating a short circuit by dumping itself in the vesc that is at 5.00V
What this also does it pulls more current from the vesc w 5.1V and that might make it drop to a equilibrium…
But this applies to any voltage rail, not just the vesc, you do not put two different supplies in // if they don’t have proper senses or ORring diodes
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Thx @Blasto or your response. Especially the connectors going directly to the STM are very sensitive and have a very low tolerance to over voltage/current and this is why @Nowind fried the STM, although he disconnected the 5V from one cable.
If you Y your STM/DRV will likely fry!
Frank
So you admit to split PPM not being an issue. It’s split 5v that’s a problem.
Yup for sure. Wouldn’t have it any other way.
Here’s an idea based on what you said: One remote paired with 2 separate receivers connected to 2 seperate Vescs. Bet no one has tried that yet. Anyway, as I said before, I’ve been running dual Vescs with split ppm for over a year with no problem. NOTE: I did clip one of the 5v wires to be safe although what @Jinra said about parallel makes sense.
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I concede that I’m not familiar with electronics enough to understand what @Blasto said, but I’d trust him enough with it.
For me anyway I just simply soldered another wire to the PPM on my servo to make a split PPM signal, no need for the other 5v or GND.
I was just being stupid
In my mind this would seemingly eliminate the problem that @trampa is saying which is over current/voltage with the Y splitter. Why doesn’t 2 receivers work when one does if both the one recover and 2 recover have the same 5v cable going to a vesc?
So cut the single 5v.
i just feel like that the ‘likely’ term you used has been proven wrong by the amount of people that actually do use a y-split and not had any issues… but please if anyone else has seen other cases of dead vesc from using a y-splitter post it here…im going to be setting up double vesc soon and already fried one doing a CAN connection…so in my mind im more ‘likely’ to fry it by can-bus…but thats just in my own experience…
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And experience is the best teacher.
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My electrical engineering background is limited to some 2 semesters of study (I barely passed) some 15 years ago… Please excuse my ignorance.
The PPM signal coming from the receiver is a series of 5v pulses. The receiver is powered by one of the VESCs, because you cut one to prevent the short (based on what I’ve read above). Based on what @Blasto said there could be some variance in the VESC voltage, so the receiver may be powered by 5.0v or 5.1v. Does this mean the PPM signal sent by the receiver will be either 5.0v or 5.1v depending on which VESC it is connected to? And does the VESC outputting 5.0v care if it receives a PPM signal at 5.1v?
Agree to some extent, however I still like to understand how/why something works.
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No the mcu does not care if the ppm signal is 5.0V or 5.1 (if i remember correctly the IO’s of the stm32 is tolerent up to 5.3V)
What i am saying is by connecting two power rails in // it could unbalance one or the other buck converter (on the DRV) and that’s where shit can hit the fan by bringing the voltage over 5V or damage the DRV’s buck converter.
Side note, // = parallel because im a lazy fuck
The ppm signal is not 5v. Only the 5v middle rail is 5v. I forget the exact voltage of the ppm wire but it’s at least 2v lower than that. Which begs the question of why the minute difference in ppm voltages is fine for parallel ppm but not for the 5v rail @Blasto
PPM Y cable with 1 red wire unpluged has been working good for me on vesc 4. I like the redundancy, I can still get home on one motor if need be.
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Thanks. Yeah, bit of Googling showed that the signal is regulated to some other voltage. Mostly 3.3v. Given the VESC must be tolerant to a range of PPM voltages I’m back to struggling to see how the Y cable could break stuff.
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Back when I was considering using hobby Esc’s with built in BEC, I heard somewhere that it was necessary to clip the red wire from on of the Esc’s in a dual configuration. When I started using Vescs, I just carried that principle over. Better safe than sorry. @Jinra Have you actually tried running dual vescs in a Y ppm setup without clipping one of the 5v wires?
No since i use a standard 3 pin servo cable and attach a single other cable to the PPM wire via solder.
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Correct, normal esc need to pull one possitive lead. So tat receiver oni send signal to esc. I make this mistake before. Fried my esc.