my home made inverter circuit

[Nickk2057]

and on whick part of the diagram to put that resistor parts?

[c4757p]

they are radioshake brand... i will have to be sure tho

I'm not saying they're unreliable or counterfeit or anything - even good capacitors often have awful tolerance. -20% +80% is not uncommon for electrolytics.

and on whick part of the diagram to put that resistor parts?

Huh? Replace the 4.7k ones.

[Nickk2057]

and i will try that in a bit...


will see what happens

[Nickk2057]

the caps are nichicon 2.2uf 50v B P.... 85*C 1115 PET

[c4757p]

If you're wondering, here is the datasheet for those caps. Tolerance is 20%, so that allows your nominal 70Hz frequency to be anywhere from 56Hz to 83Hz. Aren't capacitors wonderful?

[Nickk2057]

so if i use higher resistors it will get lower in frequency.. so if i use the pots on them instead of the resistors i can adjust them to the level i want... and also find the sweet spot to use too.... plus when i find that sweet spot i will check the resistance on the pot to find the resistor i need

[Nickk2057]

and yes... caps are VERY wonderful XD

[c4757p]

so if i use higher resistors it will get lower in frequency.. so if i use the pots on them instead of the resistors i can adjust them to the level i want... and also find the sweet spot to use too.... plus when i find that sweet spot i will check the resistance on the pot to find the resistor i need

Sure, but remember that the ideal resistor in this circuit is 5.4k. The only standard (E12) values in that neighborhood are 4.7k, 5.6k and 6.8k, which give nominal frequencies of 70Hz, 58Hz and 48Hz respectively. No matter what that pot ends up at, the closest fixed resistor is always going to be 5.6k, unless those capacitors are way the hell out. You can combine resistors to get different values, but come on - the frequency isn't that critical.

[c4757p]

If you're wondering, here is the datasheet for those caps.

Actually, I'm not so sure that's the datasheet any more - it says they have a PVC sleeve, but the sleeve on yours is clearly stamped PET. (There are also actual PET capacitors, but those are not, they're bipolar aluminum electrolytics - Nichicon never made film caps that look like that.) I can't find any other Nichicon caps that meet those specs, though, so I can't find the real datasheet. Whatever they are, they seem to be a discontinued part, so it's hard to find information on them. Anyway, I can make out a (M) on one of them, and that's the tolerance specifier - 20% - so at least that part was right.

I really wish they'd just stamp the full, proper part number on the things. There's obviously room for it.

[Nickk2057]

haha... yea i know... you know it be great to talk with you in person... you sound like a great person to talk to as well.... of how smart you are on those things.. it be great to talk with you so we can help share information if you like that is

[c4757p]

I'm surprisingly boring in person.

[Nickk2057]

now who would of said that? >_> the way you talk on here you sound like a smart person.... anyways.. i will try that out with the 5.6k resistors... just hope it works.. but now i ran out of those IRF chips

[Nickk2057]

now i got to get some more ordered... hope they are cheap.... and i HOPE i don't have to order them from china... takes forever to get here

[Nickk2057]

i probably have to make a reinforcment thing to keep the IRF chips steady on the board thats also on the heatsink

[c4757p]

now i got to get some more ordered... hope they are cheap.... and i HOPE i don't have to order them from china... takes forever to get here

Order from Mouser. IRF3205 is $1.70 each. There are a ton of similar parts - for an exact equivalent, they are all about the same price, but if you're willing to go a bit lower on some of the specs (IRF3205's 110A maximum current is probably a bit excessive, for instance), you can get them cheaper. IPP093N06N3 e.g. is $0.78, but only 50A.

[Nickk2057]

does this sound right? http://www.ebay.com/itm/IRF3205-BY-IR-LOT-OF-20-/160605834301?pt=LH_DefaultDomain_0&hash=item2564da8c3d

[c4757p]

It's definitely the right part. It's a suspiciously low price, but then, they do have excellent feedback. I'm not sure - I'd probably take the chance if I were in a good mood.

[Nickk2057]

well until i get my next paycheck i will defenantly get it... i am out at the moment till i get the MOSFETs... but that will give me time to work on the oscillator

[Nickk2057]

hmm... i found an old inverter thats broken and i can salvage the mosfets from that AWESOME... now to work on that project.... and maybe i might use a resistor between the gates and the oscillator... it might be a good idea i guess

[Nickk2057]

ok... i wonder if there is the datasheets for the IRF1404 and the IRF640... and what the amps are going to be

[c4757p]

hmm... i found an old inverter thats broken and i can salvage the mosfets from that AWESOME...

Yep. I pretty much dive upon old shit that I can salvage from like that.

and maybe i might use a resistor between the gates and the oscillator... it might be a good idea i guess

Sometimes this is a good idea, but it's not good to just sprinkle resistors about because you've heard of it. Why do you want it? You already have a resistor between the gate and Vcc.

[c4757p]

ok... i wonder if there is the datasheets for the IRF1404 and the IRF640... and what the amps are going to be

So what kind of Internet connection gives you EEVblog but not Google? 

[Nickk2057]

LMAO!!! haha.. yea.. i got it now.... the 1404 has up to 75 amps and the 640's has up to 18....which one will i pick? well... you will have to figure that out

[c4757p]

Besides that - 1404 has a lower resistance. 640 has a higher voltage rating (significantly). 640 also has half the gate charge, which means you'll be able to switch it faster (not really a concern unless you're doing high frequency stuff). 1404 is rated for higher power, but you're not getting anywhere near the maximum of either one without one hell of a heatsink anyway.

[Nickk2057]

well.. i got it.... and with the 1404 MOSFET's.. and working like a charm too