Active pre-charge/inrush control

[fechter]

The source has to go to the switch somewhere. I don't see the connection.

 

[izeman]

source goes to battery negative and to the right pins of the fets. or do you look for something else?

 

[fechter]

source goes to battery negative and to the right pins of the fets. or do you look for something else?

It's hard to see the blue trace in the layout. If it connects to the zener, then it would be OK. To me it looks like it isn't connected. Everything else looks good.

 

[izeman]

source goes to battery negative and to the right pins of the fets. or do you look for something else?

It's hard to see the blue trace in the layout. If it connects to the zener, then it would be OK. To me it looks like it isn't connected. Everything else looks good.

i don't get it you're talking about the dark blue or the cyan one? neither one is connected to SOURCE. cyan is GATE and SOURCE is yellow which goes to zener negative and zener positive goes to GATE.

 

[fechter]

Don't worry, I think I was just having a retarded spell.

I just wasn't seeing where the source line was going to the switch, but if you're just coming off the battery connection, that works fine.

I was also a bit confused by the 12V line. It seems to just pass through without connecting to anything.

 

[izeman]

Correct. 12v is only there to feed the switch's LED.

 

[fechter]

OK, just fix the labels and make some boards!

What FETs are you planning to use?

 

[izeman]

3077 as my voltage is limited to 50v

 

[izeman]

if anybody would like to order some, here's the shared project link: https://oshpark.com/shared_projects/Wv7n4X4m
if you like it, and use it, and like it, please let me know

back side is not shown. 12V can be ignored for most. this is just for my circuit as the switch needs 12V for the led, it's just a 12V in, 12V out thing. has nothing to do with the circuit itself. the screenshot of the right side of the board is cut off a bit.

this is what v2 looks like:

 

[cycborg]

Do you have a BOM? What size are the SMD components? And is an oven needed to mount the FETs?

 

[izeman]

No BOM. all parts are found in the circuit scheme by fechter and values are printed on the pcb
2x 1M resistor
1x 1k resistor
1x 1u cap bipolar full voltage
1x 12v zener
parts can be 0805. zener is 1206.
FETs are your choice.

 

[ryerson2019]

All components purchased, with only the board left to ship.

I'll try to clarify the build process for future DIYers.

 

[izeman]

i haven't received the boards yet either. still being in the manufacturing process.

 

[rmrf]

Also ordered 3 boards, thanks for the project!
Is this board designed for 4 FETs?

 

[izeman]

I hope you looked at the pcb pictures i posted. There's only space for 2 FETs. I can send you the eagle file and you can modify it.

 

[rmrf]

Yes I looked at the pictures, pcb have copper on both sides, that's why I asked. Sorry for noob question
I think I will be fine with 2, will not exceed 50 amps

 

[ryerson2019]

I wouldn't mind the eagle file. I might try to integrate it into the next VESC I make.

 

[izeman]

50A is fine. Just use genuine FETs. Copies tend to get too warm and get shorted.
I run it a 60A max with two 3077. And you need a heatsink at the back. Or screw it to the bike's frame.
Here is the eagle link https://www.dropbox.com/s/vlkcyolgltubdip/switch_xth.brd?dl=0

 

[rmrf]

Can't find 1206 zener on mouser. Any other package that would fit?

 

[izeman]

Can't find 1206 zener on mouser. Any other package that would fit?

i guess 0805 should fit as well. those are the ones i ordered http://www.ebay.de/itm/171346154762
but if you REALLY cant find any you still should be able to use a regular thru type one and bend it's legs as needed and solder it's legs to the pads.

 

[rmrf]

Do I need to connect 2 drains with a bent copper wire (like on one of your previous attached photos)? Also it looks like there is a connection between sources but will it sustain half the current?

I might be confusing drain vs source. It's just not very clear where is battery connection and where is ESC connection.
Leftmost FET pin is battery. Middle FET pin is ESC. Is middle pin supposed to hang in the air (not connected to the board?)

 

[izeman]

unfortunately i don't have received my boards yet. they have just been sent from the factory, so i expect them to be two weeks in transit. i could have posted pics of the ready built boards then. so this needs to wait. would have made things clearer.

and i must say w/o explanation, and w/o reading the circuit it's hard to understand.

for this to be clear you need to know, that if you have the board laying in front of you, like shown on the screenshots: the left pin of the FET is GATE, the middle one is DRAIN and the right one is SOURCE. the next important thing: we don't need to connect anything to the middle pin and can remove it (wiggle it a bit, so it will fall off), as DRAIN also is connected to the backside heat plate of the fan (the one with the hole in it). if you solder the metal fin to the board it will dissipate heat very well, and you can solder your controller's negative wire (=DRAIN) just between the two fets, connecting the wire and the two fins with one blob of solder.

i was afraid that the pcb's traces are not strong enough to carry high amps, so i made two big holes (the one in the middle of the board). you can take a 6mm2 solid wire (diameter just below 3mm) bend it to a WIDE U form and put each end in on of those holes. the SOURCE pins of the FETs will not connect to the board directly. so they don't need to be bent down, and can go straight to this big solid wire, and will be soldered there. the BATTERY'S negative then gets soldered to this copper bar as well.

hope this makes it clear. pictures would have been worth a thousand words

 

[rmrf]

Thank you for explanation I didn't know that backside of a FET is also DRAIN

 

[izeman]

Thank you for explanation I didn't know that backside of a FET is also DRAIN

i don't know if this is true for ALL TO-220 cases, but at least it is like that for the 4110 and 3770 we use here most often. that is why there is an insulation layer between FETs and heatsink/case. we don't need that in this case, as the two FETs share the same level. but be careful if you connect it to your bike's frame - i did that to cool the circuit. my battery is NOT connected to the frame, so this is no issue. but if you (for whatever reason) decided to use the frame as common ground you will not be happy, as in this case you connect SOURCE = battery-gnd to DRAIN = controller-gnd and this makes the circuit obsolete.

 

[ryerson2019]

How are you powering your 12V LED? My boards arrived and I'll put them together when I'm through with finals.