# motor controller, just a few questions.

#### rcblack79

Joined May 1, 2016
20
Hello everyone, know its a simple circuit but i found this online and i want to build it for a project, but i want to squeez a lil bit more juice out of it. The volts is good but i want to change the mosfet for something better and the number of mosfets. What else should i change to get more juice. Just need some advise before i spend my money. Thanks for all comments.

#### Kermit2

Joined Feb 5, 2010
4,162
You are good to about 1/2 of a horsepower with what you have.

What is the motor rated?

Joined Jul 18, 2013
22,039
I tend to use 15v for these type of 555 controllers, you can still use this for the 12v motor also, just do not run 100% PWM.
Max.

#### rcblack79

Joined May 1, 2016
20
I have 4 -775 mico dc motors i got from a friend. Each can handle about 125 amps for 10-15 secs. 45 amps all day at 24 volts. Because i am a elec. tech. Student i have not got into integrated circuits. Ill have my A. S in November this year then ill do EE with a focus on motor controllers. I just want to get my hands wet befor i start EE and this circuit is simple and a good start. One last thing i want to parallel the motor on one controller hence the need for a more

Power

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#### shortbus

Joined Sep 30, 2009
8,197
You may need a few extra mosfets and 555's, to replace the ones that burn up. The output of the 555 is limited, to ~200mA. This means your mosfet will switch slowly and get pretty hot as a result. Driving even more than one mosfet at a time means it will get even worse. Adding a "buffer" transistor between the 555 pin #3 and the mosfet(s) gate will help.

#### hp1729

Joined Nov 23, 2015
2,304
Four 125 Amp motors? 500 Amps?
About $150.00 from DigiKey. VMO1200, 100 V, 1,200 Amps. The manufacture IXYS has a good web site with application notes. I didn't spend much time there. But it Googles easy. #### Attachments • 509.4 KB Views: 3 Last edited: Thread Starter #### rcblack79 Joined May 1, 2016 20 just some ideas that i have i guess ill wait till i start engineering school. Thanks #### DC_Kid Joined Feb 25, 2008 796 is the motor for sqeezing oranges ?? agree with shortbus, need a driver (silicon) between 555 and fet. but, 200mA of charge rate should be plenty if the fet has low gate capacitance. more amps does make it turn on/off faster though. but what exactly are you swapping? if you want more "juice" then choose a fet with very low Rds(on) value Last edited: Thread Starter #### rcblack79 Joined May 1, 2016 20 I found a shcematic for a driver circuit and im sure it will help. Im just curious of how some manufactures pack 3000 watts into a simple controller for hobby uses. If i keep looking i will find what im looking for and having these helpful conversation will guide me in the right direction. Thanks Everyone Thread Starter #### rcblack79 Joined May 1, 2016 20 Four 125 Amp motors? 500 Amps? About$150.00 from DigiKey. VMO1200, 100 V, 1,200 Amps.
The manufacture IXYS has a good web site with application notes. I didn't spend much time there. But it Googles easy.
That is a mean mosfet.

#### hp1729

Joined Nov 23, 2015
2,304

#### DC_Kid

Joined Feb 25, 2008
796
a few fets in parallel ?? this way you have some redundancy in case 1 fet goes south? better have a decent heatsink and some fans.

#### rcblack79

Joined May 1, 2016
20
You may need a few extra mosfets and 555's, to replace the ones that burn up. The output of the 555 is limited, to ~200mA. This means your mosfet will switch slowly and get pretty hot as a result. Driving even more than one mosfet at a time means it will get even worse. Adding a "buffer" transistor between the 555 pin #3 and the mosfet(s) gate will help.
I found this example of a current buffer circuit to help the with the low output of the 555, but not sure if it will work. Do i need more resistors amd what happens with the original resistor coming out of pin #3 of the 555

#### Kermit2

Joined Feb 5, 2010
4,162
I found this example of a current buffer circuit to help the with the low output of the 555, but not sure if it will work. Do I need more resistors and what happens with the original resistor coming out of pin #3 of the 555
Google a darlington amplifier. Current limit on the input base lead may or may not be needed depending on the beta value for the transistors you select.

#### rcblack79

Joined May 1, 2016
20
First i would like to thank everyone for all their help, i did look into the darlington amplfier and it is the answer to my question of how to pack more power into this simple 555 circuit. There are so many to choose from dont know what to use. Befor i draw a schematic to try to incorporate it into the 555 what else should i look into? And max safe number of transistors to use for a darlington amp? I found this will it work or is something missing