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### Author Topic: solenoid specs: duty cycle  (Read 2352 times)

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#### Jak24

• Full Member
• Posts: 96
##### solenoid specs: duty cycle
« on: May 21, 2010, 09:59:08 AM »
HI!

I'm currently looking to purchase a solenoid :
http://www.electromechanicsonline.com/product.asp?pid=24
I know i want it to be 12 vdc but I'm not sure about the duty cycle
(i need the solenoid to kick a ball, roughly every 10 seconds) i realize that the power of the kick grows as the duty cycle gets smaller and the watts increase, and just to make sure, is the 'on time' the amount of time the solenoid can be pushed out, right?
I'm using a 12v 2600mAh Nimh battery if i get the 10% or 25%  how much would that effect my battery level?
here are the specs, please suggest which one i should get.
C = Continuous (100%) Duty Cycle, Maximum On-Time = Infinite
Approximate Input Power = 8 Watts
Force at 0.05" (1.3 mm) stroke: 21.0 Oz (595 gr)
Force at 0.25" (6.4 mm) stroke: 4.0 Oz (113 gr)
Force at 0.50" (12.7 mm) stroke: 1.5 Oz (43 gr)

I = Intermittent (50%) Duty Cycle, Maximum On-Time = 180 Seconds
Approximate Input Power = 16 Watts
Force at 0.05" (1.3 mm) stroke: 36.0 Oz (1021 gr)
Force at 0.25" (6.4 mm) stroke: 9.0 Oz (255 gr)
Force at 0.50" (12.7 mm) stroke: 3.0 Oz (85 gr)
Force at 0.75" (19.1 mm) stroke: 1.0 Oz (28 gr)

L = Long Pulse (25%) Duty Cycle, Maximum On-Time = 30 Seconds
Approximate Input Power = 32 Watts
Force at 0.05" (1.3 mm) stroke: 51.0 Oz (1446 gr)
Force at 0.25" (6.4 mm) stroke: 19.0 Oz (539 gr)
Force at 0.50" (12.7 mm) stroke: 6.0 Oz (170 gr)
Force at 0.75" (19.1 mm) stroke: 1.5 Oz (43 gr)

P = Pulse (10%) Duty Cycle, Maximum On-Time = 8 Seconds
Approximate Input Power = 80 Watts
Force at 0.05" (1.3 mm) stroke: 64.0 Oz (1814 gr)
Force at 0.25" (6.4 mm) stroke: 36.0 Oz (1021 gr)
Force at 0.50" (12.7 mm) stroke: 16.0 Oz (454 gr)
Force at 0.75" (19.1 mm) stroke: 4.0 Oz (113 gr)

Regards

Jak24

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: solenoid specs: duty cycle
« Reply #1 on: May 21, 2010, 03:12:45 PM »
Hi,

[...] is the 'on time' the amount of time the solenoid can be pushed out, right?
It's the amount of time it can be pulled in (which make the thin rod poke out from the other end).

I'm using a 12v 2600mAh Nimh battery if i get the 10% or 25%  how much would that effect my battery level?
here are the specs, please suggest which one i should get.
The 10% duty cycle draws 10 times the current as the 100% duty cycle of course, but you will only need a short pulse of current for a "kick", much less than a second.
The actual time you will have to find experimentally, as it depends on the physical parameters of both the solenoid and of the ball - start with eg. 100ms and add until you get a full kick with the ball loading it.
This time (plus 10..20% for consistency) should be used for each "kick".

Assuming kicks are 1s long, and each use 80W/12V=6.7A, you would have around 1500 to 2000 kicks (assuming this battery won't be used for anything but the solenoid), so with one kick each 10 seconds, it would run for more than 4 hours.
With this high current drain, the internal resistance of the battery will limit the available voltage a bit, but you will still get the most powerfull kick from a solenoid wound for 10% duty cycle.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### Jak24

• Full Member
• Posts: 96
##### Re: solenoid specs: duty cycle
« Reply #2 on: May 25, 2010, 11:08:52 AM »
HI

could you tell me are my calculations correct ?
beside the solenoid,
I'm running three of these motors:
http://shop.maxonmotor.com/ishop/article/article/222049.xml
and 1 motor of these motors :
http://shop.maxonmotor.com/ishop/article/article/2516.800-11.111-000.xml
there continuous  torque (without the solenoid) is 2.5 Amps(0.8 x 3 + 0.1)
so if the kick is 0.5 seconds long then 80W/12v = 6.7A : 2 = 3.35A
so 2.5A + 3.35 A = 5.85A and my battery is 2600mAh, so it would last less than 30 min.
but if i get the the the less powerful solenoid (which is 32W)
then it would consume much less,.... but i don't know how much less powerful it would be :-( ?]

thanks
Regards

Jak24

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: solenoid specs: duty cycle
« Reply #3 on: May 25, 2010, 05:16:58 PM »
Hi,

[...] continuous  torque (without the solenoid) is 2.5 Amps(0.8 x 3 + 0.1)
It's not the torque, but the current draw, that is measured in Ampere
The max. continuous current is 0.853A and 0.105A respectively, which means 2.664A total max. cont. current.
However, you won't be running the motors at max. all the time (and all 4 of them).

so if the kick is 0.5 seconds long then 80W/12v = 6.7A : 2 = 3.35A
so 2.5A + 3.35 A = 5.85A and my battery is 2600mAh, so it would last less than 30 min.
80W at 12V is 6.7A
Drawn for 0.5s each 10s is 6.7A/20 = 0.335A average.
So, if all motors goes full blast all the time and you kick for 0.5s each 10s, your current draw is: 2.664 + 0.335 = 3.0A

Since your motors won't go at max. all the time, the actual current draw will be lower, how much lower will depend on driving style and environment.

but if i get the the the less powerful solenoid (which is 32W)
then it would consume much less,.... but i don't know how much less powerful it would be :-( ?]
32W at 12V will, with the same 0.5s/10s draw 0.133A and you save 0.2A (average).

The bottom line is, that the 80W solenoid will be only 11% of your max. possible current draw.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?