upgraded FETs

[Doctoraudio]

Can you sell, the listed as #4, let me know!
I will send it buy Paypal
If so email me @ doctoraudio@msn.com

[neurokinetik]

Well, I only have one FET setup right now, so as of this time, the answer is no. After the beginning of March, when the IRF4905s come in from backorder, then possibly.

[neurokinetik]

On another note, I will be trying a new battery setup using as many as four 23A batteries (12V each) with this FET setup for drag racing. It has to be a drag only setup, because I doubt the batteries will last more than a minute. :lol: I already have a 5V regulator, so now I am just waiting for battery holders before I can try it. 48V and less weight than the stock AAAs should be pretty quick. (Quickest to blow out axles, blow up motors, etc. I just want to see what happens. It should be entertaining, at least.)

[Rez]

Are there no other good suppliers of the 4905?

[neurokinetik]

I just did a search and found this...

Apparently the IRF4905 is popular among the RC community for speed controllers...

http://www.oatleyelectronics.com/kits/k161B.html

Anyway, all the big suppliers I know (DigiKey, Mouser, MCM/Newark) are out of them at the moment, so we are basically waiting for International Rectifier to make some more. Newark actually has some, but they are the wrong package type, (we want TO220AB) so they won't work.

[xxspeednplayaxx]

dear neuro,

under my thread "regulator mod by jshwwa" could you post a tutorial of how you did it, theirs a lot of confused modders out their (myself included) who would like to know the details of this mod

also how would you wire up both the regulator mod, and your fet mod together? thanx a bunch...

happy modding!

[neurokinetik]

Well, the mod needs more testing. The 12V experiment (and hence any subsequent mods that use this type of battery) portion was a failure. These 23A batteries can't provide enough current to even get the motor to turn a single revolution. Even with a big capacitor to store the energy, the motor will only turn over a couple of times then stop.

Hooking up the regulator was simple. All I did was run power from the batteries to the input and ground on the regulator. Those same connections also go to the power and ground connections on the FET board. Next, I run a pair of wires from the output of the regulator and ground to the main board. The steering servo worked fine. The way it was hooked up. I was wondering if maybe the transistors were not turning on fully, thus not allowing the motor full power, but I confirmed on the scope that I was indeed getting full power, and even when I connected the battery directly to the motor, the performance was still just as poor.

[xxspeednplayaxx]

alrighty, that seems simple enough and your fet board is the diagram on page 9..

Neuro,
I've done some poking around and IRF has made a revision to the TO-220 packaged MOSFET you have used. I think it is now possible to shrink your design by 40%.

Check it out
IRL3705NS/L
IRF4905S/L

Only a little difference between them in the Thermal Resistance.
Neuro check it out if you can I'm waiting for mine to come in. Feel free to comment if you found anything wrong with these Fet's.

THX ahead of tyme

[neurokinetik]

Originally posted by codedat
Neuro,
I've done some poking around and IRF has made a revision to the TO-220 packaged MOSFET you have used. I think it is now possible to shrink your design by 40%.

Power dissipation capability is quite a bit lower with these packages, however. 2W is actually lower than the S08 package is doing (3.5W) It is also much more difficult (if not impossible) to attach a heatsink to that package. I've had the tabs on TO220s get hot enough to melt solder, so I'd like the capability of attaching a heatsink.

Might be good for an "entry level" version of the circuit though.

Neuro, I'm confused? On their spec page it says 3.8W not 2W. Or is that just the calulations from using V from 4 AAA batteries. If so then shouldn't the original Mosfet package give you the same power disapation. (Whew I'm tired been up all night, can't stop thinking.)

[neurokinetik]

In one place it says 3.8W, but in the description at the top left, it says that package style is good for 2W. Either way, a smaller heatsink area means less power dissipation. They don't really make it clear whether the through-hole version is capable of more than the surface mount version, but the only real difference between the two is the way the legs are bent, so I wouldn't think there would be a difference.

Thanks for clearing that up I'm still finsihing up on my degree and some things are still not clear. I learned more in the forums from you then in class

[scatmanjohn01]

like this?

[neurokinetik]

Yeah, that's basically it, though technically, you don't need to show IC3 and IC4, and you should rotate the bottom side of the board so that the unconnected pins are at the top of the diagram.