On Wed, Oct 2, 2013, at 10:47 AM, andy pugh wrote:
> I guess I could use a 250W resistor, which is 30s to 5V, or a 1kW > resistor, which is 7.5 seconds to 5V. But both seem wasteful, and I am > not sure I have the space. > (Also quite expensive: > http://uk.rs-online.com/web/p/panel-mount-fixed-resistors/7014059/ ) For intermittent duty (as you are using it - connected only on power down), the cheapest high-power resistors are heaters. For example: $8 gets you 38.4 ohms, 1500W intermittent (or continuous, if wet ;-): http://www.ebay.com/itm/200960173435 That has more then enough thermal mass to handle 20,000uF at 300V. I've used 2 of those in series to discharge 24,000uF at 600V (4.8 times the energy). The flange makes it fairly easy to mount. $13 gets the same ohms and watts, but can run continuously if needed: http://www.ebay.com/itm/131001379245 Just don't put anything meltable nearby. I've seen these used as DB resistors for spindle drives - mounted in a mesh box on top of the machine so the heat can escape. -- John Kasunich jmkasun...@fastmail.fm ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users