View Full Version : my first circuit diagram...

12 January 2015, 0643
this is my first circuit diagram after reading several threads i finally dared to draw one.i'm sure there are many mistakes in the circuit,i would like to have comments and suggestions.

-most of you people choose pmdc motor along with the alltrax...but i'm going with bldc motor with inbuilt controller,it is only available option for me..in my locality it is very hard to find dealers of pmdc motors.

12 January 2015, 1146

12 January 2015, 1228
Hey Pavan, first off, that's a nice, clean diagram! There are a couple main purposes of a diagram like this, and conveying information is the first -- your diagram does that pretty well. The most important thing is that the author be able to convey information clearly and unambiguously to the reader. Since you're probably both author and reader, you're in pretty good shape.

There are a couple of stylistic things you might update, although they're not terribly important: batteries have a symbol that looks like big and small vertical bars next to each other:


You could use those to convey the information more unambiguously. Likewise, the throttle is almost certainly a variable resistor:


That's one you should definitely use, since the variable resistor has three connections, and it's pretty important which way around they're connected. If your motor/controller combo has a known set of inputs, make sure they're called out by terminal name or number, and that the wires that go to/from them are clearly showing what they actually connect to -- just having some wires going to a black-box "throttle" is ok as a placeholder, but you'll want to have that figured out before you get to trying to build anything.

Stylistically, I think the "jumping" line like you have for the lower leg of the ignition switch line is out of favor now, you can just cross the lines without putting a dot. By the same token, the leg coming off the downstream line from the contactor (to the right of the contactor) should have a dot on it, to indicate that it's really a connection (although it's hard to mistake in that particular spot).

There's a free schematic drafting program called Eagle available, which is really intended for printed circuit board design, but it also includes a good schematic diagram editor. I recommend it because there's a lot of support available for it online. Another good choice (and more free) is Kicad, although it's a much newer program and may be harder to find hints on what you want to do. An advantage of both of them is that they do some logical connection checking, and will warn you if you have things like dangling connections. I have run both on my several-year-old netbook, so they're not resource hogs.

As far as the meaning behind the diagram, you might examine the location of the switch labeled as "ignition." Based on its connections into the circuit, it could just as easily (and much more clearly) be placed below the contactor, just below the pre-charge resistor, bridging the sides of it. I'm not sure why you have a switch there, but I would move it, since that's the electrical effect it has. It seems to serve the same purpose as the ON/OFF switch, at least as drawn.

I'm pretty new to the EV game, so I can't comment on the more EV-specific stuff you've got there (pre-charge resistor, placement of fuses, etc.). If your contactor is actually a relay, you might consider using a relay symbol to clarify which connections go where:


This looks to me like a very basic system, and like you're concentrating on just the traction stuff without worrying about accessories or chargers or battery management systems. That's a good way to keep things clear, but don't forget that you have to plan for all those things as well. I obviously don't know what kind of system you're planning to build, but most of the electric motorcycles I've seen seem to want more than 200A of current from their batteries. You might think about that when sizing your conductors (fuses are easy to swap, but the whole point of a fuse is that it blows before your wires catch fire, so the fuse has to match the wires to some extent).

Don't take this list as a negative comment -- you're off to a great start, and hopefully what I'm telling you can offer some useful improvements. Wait for the real EV guys to chime in though, as I'm sure I've got some of the EV-specific stuff wrong, and my goal isn't to pass on bad advice. Have a good day!

13 January 2015, 0811
thank you ianz,
i would make necessary changes and update my circuit diagram.since i'm a mechanical engg. student i know only basics of electrical wiring i'm trying my level best to understand every circuit diagram in the forum.
----coming to BMS i think i can omit that because i'm using 4*12v*55ah AGM lead acid batteries(i think these batteries can manage..however they are only four of them) so i thought of not considering that and to keep my project with in budget.
----i'm using 200a fuse , i consulted the product manufacture and he said that 200amp fuse is good considering the controller program.however i will once again re-consult him.
----i should once again think of ignition/starter switch..
once again thank you for your comment...
once again thank you