{"id":13,"date":"2015-09-15T12:10:00","date_gmt":"2015-09-15T11:10:00","guid":{"rendered":""},"modified":"2023-08-18T12:25:04","modified_gmt":"2023-08-18T11:25:04","slug":"diy-dro-for-mini-mill-2","status":"publish","type":"post","link":"https:\/\/blog.hslracing.com\/electronics\/2015\/09\/diy-dro-for-mini-mill-2.html","title":{"rendered":"DIY DRO for Mini Mill 2"},"content":{"rendered":"

I have since had some more thoughts on this subject and after counting the connections again, decided that it could be implemented with an ATtiny85\/45\/25<\/a> DIP 8 chip.<\/p>\n

After downloading the DRO_2_2 source code from Yuriy’s website and compiling it up noticed that it will fit on an\u00a0ATtiny85<\/a>\u00a0or 45, but not on a 25 because at 2294 bytes \u00a0it requires slightly more than the 2048 bytes of memory available on the 25 chip.<\/p>\n

If I use\u00a0TinyDebugSerial<\/a>, this gives me TX only, however this is all I need and it still works with the standard\u00a0Arduino<\/a>\u00a0Serial.print<\/a>, etc functions – the TX connection on the\u00a0ATtiny85\/45\/25<\/a>\u00a0chip is on pin PB3 or Digital 3.<\/p>\n

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I ended up rotating the chip on the board for the best fit for the connections:<\/div>\n

Clock – digital pin 0
\nX Data – digital pin 1
\nY Data – digital pin 2
\nZ Data – digital pin 4<\/p>\n

After all only 7 pins are being used anyway (inlcuding GND and VCC), so a full blown\u00a0Arduino<\/a>\u00a0or dip 28 atmega328p<\/a> chip is not required.<\/p>\n

The pull-up resistors are not actually required for any of the Arduino based options as there are internal pull-ups that can be used (pinmode<\/a>(pin, INPUT_PULLUP)), and if run at 3V, then the voltage divider is not required either.<\/p>\n

The ATtiny85\/45\/25<\/a> chips can be run at 8MHz using their internal clocks at 5V or 3V.<\/p>\n

I adjusted the schematic<\/p>\n

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Circuit board<\/p>\n

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You will note that I have re-arranged the various USB cable pins in order to simplify the board layout, this also means that I can use any shielded cable that happens to have a mini USB connection at one end and replace the other end with a 4 pin Dupont connector.<\/p>\n

I ultimately decided to build it with female USB connectors so I don’t have to cut the ends off the USB connectors, which made for slightly more complex wiring.<\/p>\n

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I had to move the Z axis pin from pin 1 to pin 3 because otherwise I would need to disable the reset function and lose the ability to easily program the chip, but this was no big deal.<\/p>\n

Ensure you upload a bootloader to these chips before programming, or the fuses do not set, you may also need to slow down the communication to using JP3 on a USBASP programmer when burning a brand new chip.<\/p>\n

The 7V supply is from a telephone power supply, this is then dropped to a regulated 5V by a cheap switch mode Buck converter (\u00a38.75 ($13.50) for 10 from ebay<\/a> seller\u00a0chesk_2013<\/a>).<\/p>\n

I then also drop the 5V to 3.1V with a voltage divider for powering the scales using a 220 Ohm and 360 Ohm resistor.<\/p>\n

I could have dropped the 7V to 5V using a voltage divider as well, but was unsure how well regulated the 7V supply was.<\/p>\n

Here is the completed circuit board<\/p>\n

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Rear view<\/p>\n

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and with the voltage regulator and bluetooth modules installed.<\/p>\n

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Total cost for the parts is \u00a32.50 for the bluetooth module, \u00a30.87 for the regulator, \u00a30.10 for the 2032 holder, \u00a30.60 for the USB connectors, \u00a30.95 for the\u00a0ATtiny45<\/a>\u00a0chip, \u00a30.10 for the perf board and a few pennies for the diodes, pins and capacitors, so about \u00a35.00 ($7.50) in total. The 2032 cell came with the scales, so I am not including this in the total, although they are only about \u00a30.20 each anyway.<\/p>\n","protected":false},"excerpt":{"rendered":"

I have since had some more thoughts on this subject and after counting the connections again, decided that it could be implemented with an ATtiny85\/45\/25 DIP 8 chip. After downloading the DRO_2_2 source code from Yuriy’s website and compiling it up noticed that it will fit on an\u00a0ATtiny85\u00a0or 45, but not on a 25 because…<\/p>\n","protected":false},"author":2,"featured_media":74,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[3],"class_list":["post-13","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorised","tag-dro"],"_links":{"self":[{"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/posts\/13","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/comments?post=13"}],"version-history":[{"count":4,"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/posts\/13\/revisions"}],"predecessor-version":[{"id":176,"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/posts\/13\/revisions\/176"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/media\/74"}],"wp:attachment":[{"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/media?parent=13"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/categories?post=13"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.hslracing.com\/electronics\/wp-json\/wp\/v2\/tags?post=13"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}