{"id":42,"date":"2012-03-12T17:47:00","date_gmt":"2012-03-12T17:47:00","guid":{"rendered":"https:\/\/blog.hslracing.com\/3dprinters\/2012\/03\/12\/more-stepper-testing\/"},"modified":"2012-03-12T17:47:00","modified_gmt":"2012-03-12T17:47:00","slug":"more-stepper-testing","status":"publish","type":"post","link":"https:\/\/blog.hslracing.com\/3dprinters\/2012\/03\/more-stepper-testing.html","title":{"rendered":"More stepper testing"},"content":{"rendered":"

Looks like I may indeed have destroyed one of my stepstick<\/a> drivers due to my own stupidity, of course you can’t measure current across 2 pins, you can only measure it in-line, now the diagram did show this, but I was obviously not thinking at the time, and the description was not idiot proof!<\/p>\n

The dead driver is probably due to me shorting it out across 2 of the motor pins whilst attempting to measure the current.<\/p>\n

After yet more reading about the stepper drivers, I came across the following post<\/a> stating which current sense resistors are used on the various stepper drivers.<\/p>\n

I then checked the parts list associated with the bare board version of the ones I have and they list 0.05R – same as Pololu, not the same as A4988 stepstick.<\/p>\n

so my calculation should be: Motor Current = Vref \/ ( 8 * Rs ), where Rs is 0.05 (or Motor Current = Vref * 2.5).<\/p>\n

I was now able to accurately determine how much current was being made available, I started at 1A and worked down.<\/p>\n

I tried all sorts of settings and was becoming increasingly concerned that something else was wrong, because I could cause an axis to move in the + direction for about 180 steps and then it would simply stop!<\/p>\n

After which none of the X+ or X- buttons had any effect. I later discovered that HomeX allowed a further X+ steps (again about 180) before it would stop.<\/p>\n

I had no idea what I was doing wrong, fortunately some of the people of the reprap forum<\/a> pointed out that I was probably activating my endstops and these were preventing further movement.<\/p>\n

After tricking the board into thinking it had a normally closed endstop (simply shorted the terminals), I could now cause the motor to move in both directions (home was obviously a bit confused).<\/p>\n

<\/a><\/div>\n

Here we see the full test setup, with MicroSD card, Bluetooth module, endstop cheat and stepper motor, power is supplied by 19V laptop brick.<\/p>\n","protected":false},"excerpt":{"rendered":"

Looks like I may indeed have destroyed one of my stepstick drivers due to my own stupidity, of course you can’t measure current across 2 pins, you can only measure it in-line, now the diagram did show this, but I was obviously not thinking at the time, and the description was not idiot proof! The…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-42","post","type-post","status-publish","format-standard","hentry","category-uncategorised"],"_links":{"self":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/posts\/42","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/comments?post=42"}],"version-history":[{"count":0,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/posts\/42\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/media?parent=42"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/categories?post=42"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.hslracing.com\/3dprinters\/wp-json\/wp\/v2\/tags?post=42"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}