The extra capacity will just smooth out the current supplied a little better. They’re a bit larger than what the design calculations require, but there is no harm in that. I purchased some 3500 mF electrolytic capacitors on eBay. While I was on the site I also purchased a bridge rectifier that was way overrated for this application, but that was also cheap at only $2.50. The toroidal transformer I found came from Parts Express, and as you can see, it worked out almost perfectly for this application and was cheap as well: $29.95. Gecko also recommend not feeding their drives more than 70v, so keep that in mind too. So you need a transformer that is 20x/1.414 volts, where x is the motor voltage. Rectifying (converting AC to DC) will multiply the voltage by 1.414. So, you work backwards to the transformer. Essentially, you want a voltage that is about 20x what your motors are rated for (the Gecko site explains why, don’t worry, the Geckos won’t burn out your motor if you follow their directions). Undershoot no If “yes” the steppers requires too much voltage for the driverĪll these values were derived by formulas on the Gecko site. Idealized Outputs Power Supply Rating 2.27 amps Zener Requirement Range 15% Use clamping diode if voltage is within this percent of drives max! In my case, the design exercise was done in an Excel spreadsheet that looked something like this:ĭriver Max Voltage 80 Gecko’s max rated voltage
There is a white paper in their files section that gives a detailed description for how to design one of these simple power supplies to fit your particular step motors. I’ll be constructing a classic unregulated DC power supply along the lines suggested on the Yahoo Group for Gecko Drives. Miscellaneous parts and hardware probably cost me in the neighborhood of $15, so the total power supply cost came in at about $80. The chassis and mountings consist of a piece of 18 gauge steel, a pipe clamp, and an expander rubber pipe plug from the hardware store.
This about twice the amperage needed for my 2 little steppers based on the design work below, which suits me fine. $29.95Ījax CNC Rectifier Board: $29, has inrush protection. Transformer: Toroid from Parts Express with a 56V secondary (among several others). Here is my finished supply putting out 71.8V: perfect! Hopefully this keeps the two sets of electronics out of each other’s hair from a noise and heat standpoint.īefore beginning my own efforts at this, I spent considerable time scouring the Internet to see how others had approached the problem, and constructed a photo scrapbook of what I thought were good enclosure designs. I want want to put all of this in one standard rack mount enclosure and use another identical enclosure to hold the PC.
The stepper driver electronics consist of a DC stepper power supply, the breakout board or controller, Gecko Drives, and some miscellaneous relays needed to control things like spindle and coolant.