how to wire TIP35C for 10A+ PWM load.

[Zabb Csaba]

TIP121 VCE Sat. characteristics:

 

[Nigel Goodwin]

can i also use, 2 TIP121, to do the same job?? u know, like wired parallel..

TIP121's are darlingtons, they can't be saturated anywhere near as well as the TIP35 - essential what we're discussing here with the TIP35 is a 'super' darlington, which overcomes the limitations of a standard darlington (but is configured differently).

 

[audioguru]

Yes, you're right. It's a typical characteristics at 25 Celsius.

You cannot buy a "typical" transistor. They might not have any and you might get a "minimum" one.

EDIT: The graphs in a datasheet are for a "typical" one.

 

[settra]

well thanks allot guys after all i managed to do it, using a Digital level mosfet, using the wiring that Zabb provided! it seems that what i wanted to do, could not be done at all using a TIP35C becouse , i couldent provide nearly enough ampere to saturate it! (Cause of restrictions of space and parts). but with mosfet is way easier! i guess i should search more the next time, before doing something...

 

[Zabb Csaba]

People are lucky sometimes and can buy a transistor better than average ("typical").
Best Regards,
Csaba

 

[settra]

hello guys! i think i need your help again. So: the dc motor i am using is rated at 200watt. i did the wriing, exactly as Zabb suggested, and i used An IRL1404. http://www.irf.com/product-info/datasheets/data/irl1404.pdf
i also used abig enough heat sink. but after 1 mintue of work, the outpout of the motor starts droping , and the heat sink is hot as the sun....
i talked about it with one friend that knows a bit more and he told me that , 20A is nowhere near anything that this mosfet can handle, and that it shouldent overheat that much. ghe suggested that :
1)the controller i am using (Arduino atmega128) does not produce High enough pulses, to compeltly saturate the Mosfet, resulting in ,it, working with some on-resistance
2)cause of the high capacitance of the gate, the Mosfet might be taking some more time to de-saturate
3) if that is the case , he suggested that the frequency of the pwm might be to high ? (i think arduino defults at 1khz) , and that maybe i should lower the 1kΩ Resistor, or build a drivind circuit...

what do you guys think??? how could i adress this problems?? thanks!

 

[Zabb Csaba]

Hello,

The IRL1404 is not a "logic level" FET.
The threshold may not be low enough to saturate it with 5V.
Try something like the BUK954R4-40B for this application.
**broken link removed**

Regards,
Csaba

 

[Zabb Csaba]

You should lower the 1kΩ resistor to 220Ω too.




Regards,
Csaba