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Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
Yesterday i have done the first tests on the halfbridge coilgun and first pulse-width adjustements for best velocity. These tests are non optimized, need more careful and patient working.
So far it can pierce both sides of a can, fly through a carton box, indent a metal sheet bouncing, bounce on the opposite wall, annoy my parents saying me to be careful, leave a mark on the wall and than fall on the groung bouncing many times. To avoid dangerous bouncings i filled the carton box with plastic foam, that is very efficient to dissipate mechanical energy.
It consist in 3 halfbridge stages (with decreasing turns) and a igbt-diode controlled prestage.
4 small capbanks are used with a total energy of 240Joules (960 uf, 1440uf , 960uf, 960uf all at max 350V used usually at 300V)
a quick starting position- pulse time playing gave me the following results:
Projectile mass 7.7 g, projectile lenght 38.5 mm , blunt
Pre stage: Exit velocity/energy: 14,88 m/s 0,843 J Voltage differential :300V->50V Energy differential: 42J Partial efficiency : 2%
Pre stage+ first stage: Exit velocity/energy: 26,9 m/s 2,78 J (+1,94 J) Voltage differential :300V->220V Energy differential: 30J Partial efficiency : 6,5%
Pre stage+ first stage+second stage: Exit velocity/energy: 33,8 m/s 4,39 J (+1,61 J) Voltage differential :300V->240V Energy differential: 15,6J Partial efficiency : 10,3%
Pre stage+ first stage+second stage+third stage: Exit velocity/energy: 40,0 m/s 6,16 J (+1,77 J) Voltage differential :300V->230V Energy differential: 17,8J Partial efficiency : 9,9%
Overall: Energy comsumption 105,4J Total efficiency 5,8% Exit speed/energy: 40,0 m/s (144Kmh) 6,16 J
Halfbridge stages only: Energy consumption: 63,4J Total halfbridge stages efficiency: 8.4%
I Think that i can squeeze more firepower optiminzing starting position of the first stage and the pulsetimes. Probably more than 7 joules and 43m/s (+150Kmh) and overall efficiency more than 6% (in the 7-8% range)
Tomorrow I'm going on holyday so will restart my work after being back.
Registered Member #78
Joined: Thu Feb 09 2006, 11:27AM
Location: Sydney, Australia
Posts: 133
Sweet, 5.8% eff. . How are you measure the pulsewidths the 555s are producing? or are you just twiddling the pots for best performance? What IGBTs are you using for switching?
Overall great work. makes me want to unearth my coilgun...
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Halfbridge coilgun first light
. How are you measure the pulsewidths the 555s are producing? or are you just twiddling the pots for best performance?