Current driver/power amp for solenoid

[Lyndon]

Hi all,

I have a large solenoid that draws a maximum of 15A at 24V. I want to
be able to vary the current flowing into the solenoid so I can vary
the force it generates. I want this to be driven by DAC that has an
output voltage of 0-5V and minimal sourcing current ~100mA.

I've been thinking about power FET's or a BJT's but I haven't got much
experience in this sort of electronics so I really can't take it any
further. This system is all part of a feedback pedal design that will
provide more resitance the further you push in the pedal. We have a
potentiometer measuring pedal displacement and this goes into a
microcontroller, through a simple transfer function and produces the
output signal which will drive the solenoid. I'm stuck with the type
of current driver or amp I should use. Any advice, or links to
circuits etc., will be of great assistance.

Thanks,
Lyndon.

 

[Winfield Hill]

Rob wrote...

Lyndon wrote ...

Lyndon - have you considered using a PWM motor controller? For a
quick test Dick Smith do a $20, 20A controller which I think is
PWMable. Perhaps others may be able to expand on this approach.

I wonder if Lyndon wouldn't be better off with a geared-down motor
i torque mode rather than a solenoid. They have rather poor force
vs. displacement characteristics, whereas motors are excellent.

Thanks,
- Win

whill_at_picovolt-dot-com (use hill_at_rowland-dot-org for now)

 

[Winston]

Rob wrote...



I wonder if Lyndon wouldn't be better off with a geared-down motor
i torque mode rather than a solenoid. They have rather poor force
vs. displacement characteristics, whereas motors are excellent.

Lyndon, do you really only need pedal resistance to increase linearly
between 15% and 85% of displacement? A compression spring on your pedal
would automatically do the math and provide the proper resistance.

http://www.asraymond.com/spec/faq.asp


--Winston

 

[Rob]

Hi all,

I have a large solenoid that draws a maximum of 15A at 24V. I want to
be able to vary the current flowing into the solenoid so I can vary
the force it generates. I want this to be driven by DAC that has an
output voltage of 0-5V and minimal sourcing current ~100mA.

I've been thinking about power FET's or a BJT's but I haven't got much
experience in this sort of electronics so I really can't take it any
further. This system is all part of a feedback pedal design that will
provide more resitance the further you push in the pedal. We have a
potentiometer measuring pedal displacement and this goes into a
microcontroller, through a simple transfer function and produces the
output signal which will drive the solenoid. I'm stuck with the type
of current driver or amp I should use. Any advice, or links to
circuits etc., will be of great assistance.

Thanks,
Lyndon.

Lyndon - have you considered using a PWM motor controller? For a quick test
Dick Smith do a $20, 20A controller which I think is PWMable. Perhaps others
may be able to expand on this approach.

regards
rob

 

[Richard Freeman]

Lyndon, do you really only need pedal resistance to increase linearly
between 15% and 85% of displacement? A compression spring on your pedal
would automatically do the math and provide the proper resistance.

Why do a simple solution when a much more complex one is (not) available ?

 

[Rob]

Lyndon, do you really only need pedal resistance to increase linearly
between 15% and 85% of displacement? A compression spring on your pedal
would automatically do the math and provide the proper resistance.

http://www.asraymond.com/spec/faq.asp


--Winston

Good point - a company here that makes training simulators uses this method
sometimes in combination with rubber "bumpers".

For accellerators/throttles springs of various compression rates are stacked
on on top of the other to enhance the progressive feel. For brake pedals
rubber bumbers of different diameters / lengths are stacked up to give a
realistic feeling pedal.

This is of course irrelevant if you do need the electronic solution for
other reasons.

rob