Messed up MOSFET mod

Getting bad reception? Got questions about motors, gears, and batteries? Learn how to make it go faster, roll smoother, and more in here.
Post Reply
clxfiles
bitPlaya'
Posts: 110
Joined: Sat Jan 17, 2004 11:15 pm
Location: Bay Area, Cali

Messed up MOSFET mod

Post by clxfiles »

I tried to fet mod a zz but now I get no power to the motor. Steering still works, just not the fwd or back. Below are some pics or if they're not working, links to pics that show what I did.
Basically I took ZZ that uA modded for me a while back and tried to copy it. His is the one with the black paint on it. For the small wires to jump the gates I used the small wires that were in CAT5 twisted pair.

http://photobucket.com/albums/e81/clxfi ... =ZZTOP.jpg

http://photobucket.com/albums/e81/clxfi ... Bottom.jpg

Image

Image

So all I did was swap the 4 transistors for for 2502 fets and used the copper wire to "jump" those gates. Was there something else I was supposed to do?
Last edited by clxfiles on Wed Feb 22, 2006 1:11 am, edited 4 times in total.
SHAUN
bitDisciple
Posts: 1462
Joined: Wed Oct 05, 2005 10:35 am
Location: On the trail
Contact:

Post by SHAUN »

Pics dont work. If you dont know how to post 'em I can show ya.
1000+ post of BS.
clxfiles
bitPlaya'
Posts: 110
Joined: Sat Jan 17, 2004 11:15 pm
Location: Bay Area, Cali

Post by clxfiles »

Yeah I'd appreciate that. I'm trying to figure the images out.
clxfiles
bitPlaya'
Posts: 110
Joined: Sat Jan 17, 2004 11:15 pm
Location: Bay Area, Cali

Post by clxfiles »

Thanks SHAUN... I kept using the address in the URL rather than the property. I appreciate your help.
SHAUN
bitDisciple
Posts: 1462
Joined: Wed Oct 05, 2005 10:35 am
Location: On the trail
Contact:

Post by SHAUN »

No prob, always fun helpin out people.
1000+ post of BS.
frizzen
bitDisciple
Posts: 1729
Joined: Wed Aug 03, 2005 7:48 am
Location: Big Left Turn, Indiana
Contact:

Post by frizzen »

photobucket makes it even easier, they already have one of the 3 urls you can highlite for it that has the {img} tags. Just copy and paste that shit
Jack of all trades, master of none; yet often better than master of one.
-
End genital mutilation, don't circumcise. Restore your fore'
User avatar
crazydave
bitPimp
Posts: 6874
Joined: Thu Apr 17, 2003 9:05 am
Location: Koolsville

Post by crazydave »

Alright, I think I see your mistake, on the flipped FETs, the pin with the jumper, is it making contact with the pad? Its not supposed to. Actually now that I look again, you're also using the wrong pins.


Here, this is for bits, but it'll show you the correct way to flip the FETs.
Image
...crazy man, crazy...dig it.
crazydave's Gallery
Ratfink says: "Man, it's the craziest"
clxfiles
bitPlaya'
Posts: 110
Joined: Sat Jan 17, 2004 11:15 pm
Location: Bay Area, Cali

Post by clxfiles »

Thanks CD... I can't wait to try that tonight. Now I'm gonna be clock watchin at work all day.
I think uA must have flipped those topside fets to be sitting on their top, and connected the pin to that wire only. I thought it was connected to the pad and was sitting regularly. Hard to tell with all that black paint or whatever on it.
I was looking for that chart you posted all night, the thread that is linked from the article on FETs no longer has the pics on them. That's why I figured I'd just try to copy.

Thanks PIMP!!!!

I checked out digikey's site to buy some more fets and the ones I got last time were out of stock. Will any of the 2502's do?? The performance all seem to be the same.

Digi-Key Part Number Manufacturer Part Number Description Vendor Transistor Type Voltage-Rated Current Rating Package / Case Packaging Quantity Available Unit Price
Min Qty

IRLML2502PBFTR-ND IRLML2502TRPBF MOSFET N-CH 20V 4.2A SOT-23 International Rectifier N-Channel 20V 4.2A SOT-23 Tape & Reel (TR) 84000 0.22500
3000
IRLML2502PBFCT-ND IRLML2502TRPBF MOSFET N-CH 20V 4.2A SOT-23 International Rectifier N-Channel 20V 4.2A SOT-23 Cut Tape (CT) 4393 0.77000
1
IRLML2502TR-ND IRLML2502TR MOSFET N-CH 20V 4.2A SOT-23 International Rectifier N-Channel 20V 4.2A Micro3TM(SOT-23) Tape & Reel (TR) Non-Stock 0.21000
3000
IRLML2502CT-ND IRLML2502TR MOSFET N-CH 20V 4.2A SOT-23 International Rectifier N-Channel 20V 4.2A Micro3TM(SOT-23) Cut Tape (CT) Non-Stock 0.45000
1
User avatar
SuperFly
bitPimp
Posts: 2760
Joined: Mon May 05, 2003 6:37 pm
Location: nationwide

Post by SuperFly »

before you order those up, I'd ask CD about the P-channel vs. N-channel fets. I know nothing about them, but I think I remember you can avoid the flipping and jumpering by using P-channels in a couple spots. I may be talking out my ass, but I'm sure someone will let me know. :-)
Image
clxfiles
bitPlaya'
Posts: 110
Joined: Sat Jan 17, 2004 11:15 pm
Location: Bay Area, Cali

Post by clxfiles »

CrazyDave?? Or anyone, if you know for sure, can you "skewl" us in the proper usage?
I thought the P-Channel fets were the 6401's and were only used in the SE board. I do have a coupe of them, so if they don't need to be flipped I'll try that on my next pcb experiment.
User avatar
crazydave
bitPimp
Posts: 6874
Joined: Thu Apr 17, 2003 9:05 am
Location: Koolsville

Post by crazydave »

Yep, the 6401s are a direct swap for the p-channels.


Going by the numbers the P-channels have twice the resistance as the N-channels, hence the use of all N-channels and the flipping, but that's at a 5v rating, at the voltage we're using I don't see any difference in performance. I prefer to just use the P-channel FETs as opposed to flipping N-channels, because I can do a FET mod in 10 minutes by just doing a direct swap, and I don't have to worry about any wires coming loose.
...crazy man, crazy...dig it.
crazydave's Gallery
Ratfink says: "Man, it's the craziest"
clxfiles
bitPlaya'
Posts: 110
Joined: Sat Jan 17, 2004 11:15 pm
Location: Bay Area, Cali

Post by clxfiles »

Flipped those N-channels on 2 boards and they both worked awesome. Had a little trouble with reverse on one of them but eventually found the loose connection. Now it runs like a champ.

Also, I finally got a wheel mod to work. Swiped them off an Import Racer. There's a little wobble in front but it shouldn't be too hard to adjust. Question now is what do I do with the Import Racer body.

Thanks for all the help pimps!!!
clxfiles
bitPlaya'
Posts: 110
Joined: Sat Jan 17, 2004 11:15 pm
Location: Bay Area, Cali

Post by clxfiles »

OK, got stuck on another one last night. I used the P Channel, 6401s, in place of the fets that are turned in your diagram, and the n channels on the ones they were jumperred to. I didn't swap the last 2 at all. I don't get any power to the motor or steering. Was I supposed to jump anything? I didn't, I just swapped the old trannys out and the fets in, lead for lead.

This is on a bit clone pcb that was the same layout as the diagram.
Post Reply