upgraded FETs

[mod_o_matic]

Aright! Its true, the Fets just don't cut it! But now, i must find working fets! Due to the fact i live in Canada i dont think Digi-Key can help me out BUT, you people can! http://www.e-sonic.com is a site that i can get stuff from...can someone lead me to the right direction of what fets i should buy?!

BUT, thanks for all the help!

[Jshwaa]

I'm on AIM, cuz I hate MSN Messenger and hotmail....but anyway.

I recommend IRF-3205's for N-channel, and IRF-4905's for P-channel.

[mod_o_matic]

GAAA...i have no clue what those are!! At digi-key there is like 10 and in my store, there are NONE!!

What fets do i look for? What package?

PLEASE, just look at the site above and tell me which ones!(http://www.e-sonic.com)

[Jshwaa]

You want TO-220AB package style. Screw e-sonic, they don't have squat compared to digikey. Digikey owns.

[mod_o_matic]

GAAA...man...i am 14, have no credit card and i dont really like my parents...SO NO DIGI-KEY!!!

IS there anything that would work from http://www.e-sonic.com due to the fact i can take a bus down there?! OR, if you want you could send me some up here in Canada

[mod_o_matic]

Well, i found the N-Channel, and there $ CND BUX EACH..GAAA

Are there any i can use THAT WILL WORK on this page?
http://www.e-sonic.com/acc/products....groupname=Fets

[jon.jon]

Originally posted by mod_o_matic
Well, i found the N-Channel, and there $ CND BUX EACH..GAAA

Are there any i can use THAT WILL WORK on this page?
http://www.e-sonic.com/acc/products....groupname=Fets

Do they keep anything in stock?

[mod_o_matic]

Heh, well, there not even the right ones! There should be a list of TO-220 AB..at the top find it and press refine search...


IRF1010E
IRF1010N
IRF1104
IRF1310N
IRF3205
IRF3315
IRF3415
IRF3710
IRF520N
IRF5305

These are the ones...all except two are in stock..which ones can i use?

[Jshwaa]

Use one that is an N-channel, and one that is a P-channel. I've said this before. If you're THAT lost about it, maybe you ought not try this.

[mod_o_matic]

Well, i am not THAT lost..i made one, but i used the wrong choice of FETs which made my setup lose all the energy (4.8 volts to like 1 volt!) So i dont want to make the mistake again...if i use any of the FETs listed above (2 each N and P channel) it should work? I just need some advice on what to look for in a FET...like is there certain things too look for such as voltage or something eles?

What dose PD mean (Power Dissipation)? What PD do i want, and dose it really matter? I am gessing lower is better, as it means how much power is LOST? Someone please tell me! Also, what is the most likly higest ampage i would run with an xmod? Like 5 Amps of so?

I know i can do this, it just that the FET itself is hard to find..Digi-Key would need a 16 S+H fee, and well, that is a big waste...so the best i can do is e-sonic due to the fact the have a Web site AND i can take a bus there...

[Jshwaa]

What dose PD mean (Power Dissipation)? What PD do i want, and dose it really matter? I am gessing lower is better, as it means how much power is LOST? Someone please tell me! Also, what is the most likly higest ampage i would run with an xmod? Like 5 Amps of so?

The higher the power dissipation the better. That is why I went with TO-220 and TO-262(tabless TO-220's). You'll probably be pushing 1 or 2 amps continuously, maybe more if you have a hotter motor, but the higher the current rating of the FET, the better. R(DS) is an important factor. R(DS) is the resistance the FET will present to the current flowing through your motor when the FET is on. Another important spec is V(GS) on. That is the voltage needed to fully turn the FET on/off. If you don't achieve that voltage, then the FET will always be resistive(half on/half off) and will short your cells through the FET's, thus seriously robbing your motor of current, and causing your FET's to heat up and your cells to die quick. In other words, it'd be terribly inefficient.

IC1 is the integrated circuit inside the xmod that signals the FET's to turn on/off. IC1 will only provide 3.4V to drive the FET's. Higher wattage FET's usually need V(GS) levels of 10V to fully drive the FET, or at least as high as the voltage it will be switching on/off. So if you have 7.2V from drain to source, it's best to have a V(GS) signal of at least 7.2V. If you have 7.2V from drain to source, but only have 3.4V signaling your gate(V(GS)), then that's where you're going to be running into FET's heating up, motor's hardly driving, and cells heating up and dying quickly.

[mod_o_matic]

wow man, your a god..that just explained everything i need to know on how to get the right FET

*bows down*

edit: tabless..meaning no tabe attached to the G (center pin) thing with the whole in it?
edit2:

Is there a list, or some fets people have used and worked on a 7.2 volt system, useing little lower ampage, max being 8 or so..

jon.jon: Which ones have you used?

[Jshwaa]

edit: tabless..meaning no tabe attached to the G (center pin) thing with the whole in it?

Correct, but the tab is typically tied to the drain.

Is there a list, or some fets people have used and worked on a 7.2 volt system, useing little lower ampage, max being 8 or so..

Just because you are running lower amperage, doesn't mean that you need a lower rated FET. The higher amperage FET's are able to achieve their amperage because of their low resistance. Lower resistance means you can run more current without dissipating too much power in the form of heat. If the resistance is higher, that means it will heat up sooner.

[mod_o_matic]

I see...less heat=no heatsink...

So now, i read, that i could just use all N channel or all P channel i belive,,that means i could just use 4 IRF3205 with the digram stated befor in this thread?

[Jshwaa]

So now, i read, that i could just use all N channel or all P channel i belive,,that means i could just use 4 IRF3205 with the digram stated befor in this thread?

I didn't see the diagram, but yes, you could use any variation of FET's you like, as long as your logic is consistant. In other words, if you have an H-bridge which is set up to run with 2 N channel and 2 P channel, all you'd need to do to change it to an all N channel H-bridge is to invert the signals leading to the P channels and then put N's where the P's were. And vice versa if you wanted an all P-channel H-bridge. I'd go with all N-channel if I were you though. N channels are inherently lower in resistance than P. 4 IRF3205's would work great.

But remember your gate driving. You'll need to amplify the signals leading from IC1 to drive the gates of the IRF3205's, because I believe they want 10V V(GS)on.