Harbor Freight/Chicago Electric Welder 90A modifications

So I installed a fan the one side to keep the welder cooler and increase the duty cycle. Next step is adding bridge rectifier, capacitor, and various voltage spike protection.

Coilgun update

So update on the coilgun with some pictures. Charging circuit is done. I used Uzzor's modified Mazzili driver
To charge the capacitor banks to 375V.  I got this idea from Jason's 1.25kj coilgun. Actually his coilgun was the inspiration for mine. Things I'm doing a little differently are: 3 stages (2 optically triggered) with less energy per capacitor bank, shorter slug about .30 caliber, a 14.4V 2100mAh NiCd battery instead of his 12V NiMh. I will also have a bolt mechanism like a rifle to position the slug in the initial coil.  All cap banks will have to be charged separately due to not wanting them hooked together when firing so a switch will separate them. The optically triggered stages will be designed based on the time the slug is in the coil determined by initial velocity (from the previous coil) of the slug. This should make the coilgun much more efficient and achieve a greater final velocity. Stage 1 will have only about 1000uF capacitor bank while the following 2 stages have a 4800uF bank. All capacitors are charged to 375V which is 75% of the working voltage of these capacitors.  More theory and details to follow but as for now, some pictures of the coil winding, capacitor bank building and the battery pack building.

Harbor Freight/Chicago Electric Welder 90A modifications

When striking an arc with the wire, the wire feed motor suffers from a temporary slowdown as the current draw is large for the weld and the voltage sags for a second at first.  The power for the wire feed comes from the secondary of the main transformer.  It's no load voltage is around 24 something volts AC.  Once an arc is struck the voltage goes down significantly. The first idea was to place a capacitor on the output of the bridge rectifier on the motor control board.  This resulted in the motor remaining on after the trigger was pulled and not turning off.  Must have had something to do with how they control the motor speed... my second idea was a series inductor in line with the motor and it WORKED.  You don't want a capacitor across the motor because it will slow down startup and make the motor run longer after the trigger is released.  With a series DC inductor in line with the motor it helps to provide constant current to the motor when an arc is first drawn. I wound the inductor on a ferrite toroid from a atx psu.  It's wound with 20ga wire and measures around 120uH.  It's a simple fix and the first of a series of fixes to the Welder.  

Harbor Freight/Chicago Electric Welder 90A modifications

So many of you probably have this cheap flux core welder from Harbor Freight.  It welds a million times better after switching from the cheap hf wire to Lincoln, but it still leaves a lot to be desired.  After quick inspection I discovered that the Welder outputs AC. Anyone that knows anything about flux core welding knows that the electrode should be negative polarity in order for a good penetrating weld and little spatter.  I have decided to rectify and filter the output of this Welder in order to make it into something better than just a cheap entry level Welder.  

This website has proven instrumental in helping me convert my Welder. 

Coilgun

So I'm designing and building a coilgun which uses electromagnetic energy to propel a projectile forward at a reasonable velocity.  A capacitor bank which stores energy is discharged through a solenoid which has been finely tuned for a specific ferromagnetic projectile.  The coil's magnetic field in theory has collapsed by the time the projectile enters the center of the coil and the projectile continues through the other end of the coil at some velocity.  I'll be updating pictures and maybe a few videos of the progress/project.