Need some help controlling a coil

Thread Starter

ELECTRO1234

Joined Oct 23, 2015
3
Hello all,

I have been working on a project controlling a coil to attract a metal bal at high speed.
I measure the speed of the ball in front of the coil and then decide how fast i want the ball to excelerate because the speed it need to have when it leaves the coil is about 10 m/s.
I found out i have about 9 miliseconds to use the coil. So what i was thinking is ill use a MOSFET and a pwm signal in this way i can change the dutycycle and then control the coil like in the drawing.
But i red on a site if i want this to work i need to switch high side and low side because else the coil still will be magnetic. now is my question: does somebody know what they mean and how does is work since i have not much experience with coils.

Specs:
PWM signal : 3.3v 10Khz
Coil: 51v 16A


Thank you in advance
Naamloos123.jpg
 

pwdixon

Joined Oct 11, 2012
488
Are you trying to make a rail gun?
If you are then there's probably websites for that but I would have thought there might be a forum rule against that kind of project.
 

Thread Starter

ELECTRO1234

Joined Oct 23, 2015
3
Are you trying to make a rail gun?
If you are then there's probably websites for that but I would have thought there might be a forum rule against that kind of project.
no its for my internship, it will become a closed system
 

pwdixon

Joined Oct 11, 2012
488
In any case it sounds very like a rail gun so perhaps a site about rail guns (and there must be many) might actually be helpful.
 

Thread Starter

ELECTRO1234

Joined Oct 23, 2015
3
In any case it sounds very like a rail gun so perhaps a site about rail guns (and there must be many) might actually be helpful.
yea i have looked for those site's , also coilgunsites but the problem is with a coilgun and railgun u dont want to control the coil u just want it to fire it as fast as possible
 

pwdixon

Joined Oct 11, 2012
488
yea i have looked for those site's , also coilgunsites but the problem is with a coilgun and railgun u dont want to control the coil u just want it to fire it as fast as possible
That might be a matter of trial-and-error on pulse sizing for a given setup.
 

ronv

Joined Nov 12, 2008
3,768
Hello all,

I have been working on a project controlling a coil to attract a metal bal at high speed.
I measure the speed of the ball in front of the coil and then decide how fast i want the ball to excelerate because the speed it need to have when it leaves the coil is about 10 m/s.
I found out i have about 9 miliseconds to use the coil. So what i was thinking is ill use a MOSFET and a pwm signal in this way i can change the dutycycle and then control the coil like in the drawing.
But i red on a site if i want this to work i need to switch high side and low side because else the coil still will be magnetic. now is my question: does somebody know what they mean and how does is work since i have not much experience with coils.

Specs:
PWM signal : 3.3v 10Khz
Coil: 51v 16A


Thank you in advance
View attachment 93353
People are right. The diode will keep the current going in the coil for a while.
You can reduce this time by allowing the voltage to rise higher than what the diode will allow. Think zener diode.
But with a 64 Mh coil you can only get a current of about 6 amps in 9 ms. :(
 

Alec_t

Joined Sep 17, 2013
10,359
I think ronv means a 74mH coil. You wouldn't have house-room for a 64MH one :D.
 
Top