Robin2 Posted February 5, 2014 Share Posted February 5, 2014 It might be worth pulling the enable pin low with a suitable resistor (10k?) and when the Arduino is ready it can make that pin high. Obviously that uses an extra Arduino pin. The resistor may not actually be necessary. ...R Link to post Share on other sites More sharing options...
chaz Posted February 5, 2014 Share Posted February 5, 2014 I have just started my new On30 layout (FVRR) which uses a Peco TT in the staging area. I had originally intended to use the 0-5-0 to turn and line up the TT but this is proving tricky. Due to the impossibility of getting my eye into a position to sight along the rails and the overhang of a Bachmann ten-wheeler when on the table I realised that some sort of accurate drive is going to be necessary. So discovering this topic and the solutions discussed are most timely. Excellent stuff boys! I will study at leisure and may come back with some questions (I know nothing about Arduinos). Keep up the good work. Chaz Link to post Share on other sites More sharing options...
Simond Posted February 5, 2014 Share Posted February 5, 2014 Robin Thanks for the thought - it looks like it is a "not-enable" pin, it's pulled to gnd by an internal resistor, so I'd have to pull it high to stop it - which seems a bit odd, I'm not sure why this would go high as the Arduino boots up, any sooner than the step which should stay low by default. What I might do is explicitly drive the step pin low right at the beginning of the program. There's also a sleep pin, but this is pulled up by an internal resistor to VDD - I guess I could pull this down, but the same argument applies. I'll have a play and see what I can find out! Meanwhile I'm planning to get a hall sensor to set an automatic "zero point" when I turn it on. Will advise when done. BR SD Link to post Share on other sites More sharing options...
Robin2 Posted February 5, 2014 Share Posted February 5, 2014 Robin Thanks for the thought - it looks like it is a "not-enable" pin, it's pulled to gnd by an internal resistor, so I'd have to pull it high to stop it - which seems a bit odd, I'm not sure why this would go high as the Arduino boots up, any sooner than the step which should stay low by default. What I might do is explicitly drive the step pin low right at the beginning of the program. SD Sorry, I always get those mixed up. I should have said use a resistor between enable and V++ to pull it high. The problem is that the Arduino starts with its pins low so the stepper is enabled by default when it would be better for it to be disabled. ...R Link to post Share on other sites More sharing options...
Simond Posted February 6, 2014 Share Posted February 6, 2014 Thanks Robin, I'm a bit perplexed ( haven't actually done any tests, busy day yesterday and I really didn't have the urge - zombied-out in front of TV...) because my setup sends individual pulses to the STEP input on the A4988, so if it boots up with all pins low, where do the spurious steps come from? Will have to take things apart, which I don't fancy as it's all now neatly installed underneath the t/t... I might wait until the Hall effect sensor arrives, as I'll have to have it all apart to install that. You put your sensor on the outside of the pit, and your magnet on the table - logical! - but I wonder how far away you could have sensor and still get a reliable switch point. The Metalsmiths t/t is mounted on an MDF pit, and I don't really fancy digging up the reasonably-well scenic-ed bit to install it. I can hide it under the centre of the table reasonably easily, but then it's angular discrimination will be much less than if it were mounted at the edge. I wonder if I could just stick it down in the pit somewhere and paint it to match the gravel, and hope nobody notices.....? Anyway, out tonight with the boys for a pint and a yarn, might have a try over the weekend. Best SD Link to post Share on other sites More sharing options...
Robin2 Posted February 7, 2014 Share Posted February 7, 2014 Thanks Robin, I'm a bit perplexed ( haven't actually done any tests, busy day yesterday and I really didn't have the urge - zombied-out in front of TV...) because my setup sends individual pulses to the STEP input on the A4988, so if it boots up with all pins low, where do the spurious steps come from? I sympathize. I don't understand why either. I haven't noticed this problem with my steppers - but I haven't used them much yet. ...R Link to post Share on other sites More sharing options...
Simond Posted February 7, 2014 Share Posted February 7, 2014 Robin Sorry, must have been a bad day yesterday - question about hall sensor would make more sense for Ray /Tender! I'll put it in the right thread! SD Link to post Share on other sites More sharing options...
Simond Posted March 2, 2014 Share Posted March 2, 2014 Jeff, all I've started a thread to post Arduino programs / sketches / etc. - link in my signature below. will link it back to this thread and will post the program for my t/t hope it's of interest. best SD Link to post Share on other sites More sharing options...
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