Hello all. I am new to this forumn and I was really impressed with the sharing of ideas and information here. I am doing a project that has brought me to a point where I need some outside help and I was hoping to get some ideas/feedback from people here.
First to give you a little back ground on my project, I am a hobbyist that is building a super sized ELECTRIC FOOTBALL Board. Yes thats right, an old school game from the 60s-80s where the metal board vibrates and the football players scoot across it. What I want to drive the vibration of the metal field is an electormagnet run on AC power (similar to how the old Tudor company did it in the past). However, I need a more powerful electromagnet than what was used back in the day because my supersized field is much larger and more structural. After many various types of motor sources, I have come to the conclusion that the linear vibration I get from an electromagnet (on AC power) is the absolute best thing for the job (for vibration characteristic purposes). I've had some early success of vibrating my field with a coil that is ~550 wraps, 24 guage wire (~2.5 ohms) around a spindle with a cold rolled steel core. My main problem is [1] overheating...when power is supplied by a rail power 1370 (19VAC, 18VA) I get the magnetic power I want but the coil gets really hot to touch within 90 seconds. It doesn't seem to cause major damage (yet) but it seems too hot. FYI, I measured the voltage and current across the leads of the coil is ~16VAC and 2.5A (which surprised me because isn't that higher than the 18VA power source??). Then I got a 9VAC/1A power wall transformer and then my second problem arrose...I seemed to [2] damage the transformer which I believe may be due to inductive kick back voltage that my low voltage transformer couldn't handle.
Now on to my questions:
(1) The duty cycle on this electromagnet is 30 seconds ON (max) and 30 seconds off (MIN). Do you have any suggestions on what max current I should strive for in the coiled 24 guage wire so that I do not overheat and cause serious damage.
(2) Should I be worried about inductive kickback damaging my power supply? If this truely is a concern then what would be the best recipe to disipate that energy coming from the coil when the switch is turned off. I've read about a diode and an RC snubber...I could really use some specific values on these circuits if its not too difficult.
I am a mechanical engineer not electrical engineer so forgive me if any part of my question seems dumb, or incorrect in any way. Having said that, please do not refrain from being very technical in a response as I am trying to be as resourcefull as I can to best understand a good solution to the excess heat and potential inductive kickback problem. If you find my project interesting and can my questions seem simple than I would appreciate any feedback you could give me.
Thanks!
Joe
First to give you a little back ground on my project, I am a hobbyist that is building a super sized ELECTRIC FOOTBALL Board. Yes thats right, an old school game from the 60s-80s where the metal board vibrates and the football players scoot across it. What I want to drive the vibration of the metal field is an electormagnet run on AC power (similar to how the old Tudor company did it in the past). However, I need a more powerful electromagnet than what was used back in the day because my supersized field is much larger and more structural. After many various types of motor sources, I have come to the conclusion that the linear vibration I get from an electromagnet (on AC power) is the absolute best thing for the job (for vibration characteristic purposes). I've had some early success of vibrating my field with a coil that is ~550 wraps, 24 guage wire (~2.5 ohms) around a spindle with a cold rolled steel core. My main problem is [1] overheating...when power is supplied by a rail power 1370 (19VAC, 18VA) I get the magnetic power I want but the coil gets really hot to touch within 90 seconds. It doesn't seem to cause major damage (yet) but it seems too hot. FYI, I measured the voltage and current across the leads of the coil is ~16VAC and 2.5A (which surprised me because isn't that higher than the 18VA power source??). Then I got a 9VAC/1A power wall transformer and then my second problem arrose...I seemed to [2] damage the transformer which I believe may be due to inductive kick back voltage that my low voltage transformer couldn't handle.
Now on to my questions:
(1) The duty cycle on this electromagnet is 30 seconds ON (max) and 30 seconds off (MIN). Do you have any suggestions on what max current I should strive for in the coiled 24 guage wire so that I do not overheat and cause serious damage.
(2) Should I be worried about inductive kickback damaging my power supply? If this truely is a concern then what would be the best recipe to disipate that energy coming from the coil when the switch is turned off. I've read about a diode and an RC snubber...I could really use some specific values on these circuits if its not too difficult.
I am a mechanical engineer not electrical engineer so forgive me if any part of my question seems dumb, or incorrect in any way. Having said that, please do not refrain from being very technical in a response as I am trying to be as resourcefull as I can to best understand a good solution to the excess heat and potential inductive kickback problem. If you find my project interesting and can my questions seem simple than I would appreciate any feedback you could give me.
Thanks!
Joe