Videos - The Coin Bot

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00:00:00	welcome back everybody you saw in the last video that I created a compliant mechanism that allows you to grab onto a penny and then release it appropriately so I'm pretty happy with the way that turned out and this is what
00:00:14	it looks like when it's actually put in that rotational coin slider that I've been talking about over the last few videos and you can see that that compliant mechanism Works in all three positions now so so that's pretty
00:00:25	exciting I was really happy with the way this works I can actually show you that holds on to a penny pretty well we can put a penny in there once we push that button down we can hold it it's in there pretty solidly I can shake this
00:00:41	pretty well and it won't fall out and when we rotate through these positions and we have a cog we can push on that and it will release in my original design I had this rough idea for the coin slider and it had a gear in the
00:00:56	center here that we could use to rotate the whole mechanism I was initially thinking about doing that with a clutch mechanism and I built this little prototype here so that I could show how that works I was planning
00:01:08	on showing you this in in this video how this how this was planning on working the idea was to allow this to rotate only in One Direction and that outer gear would be stuck in the other direction in that way
00:01:25	I was thinking I could use only one stepper motor to run the whole robot my idea was to reduce the part count but really we're not there yet I don't think we need to worry about that quite yet but you could see how this clutch
00:01:39	mechanism was going to work it allows the the coin slider to work in One Direction and then the sorder to rotate in the other direction without without that moving and the way that would work was this gear on the center of this
00:01:54	piece would mesh with with this gear here and we could actually use a stepper motor so once those two are meshed up you can see that I can rotate these through positions through the three positions just by
00:02:14	rotating this piece down here if I'm rotating this you can see that that actually rotates the coin slider so that was my my big plan was to use that clutch mechanism to rotate this and make sure that this this rotated one
00:02:32	way and the coin sort rotated in the other so you can see again how that works and it would have I think that would have worked pretty well but again for right now it's just a little too complicated and I think I can get rid of
00:02:44	a lot of this mess by just adding another stepper motor so that's great but at any rate um what I'm trying to show here is that I wanted to incorporate this mechanism into whatever design I had for pushing down on these
00:02:59	cogs and the first one that I came up with was was this and you can see that that that clutch mechanism still slides into place there I can put the the coin
00:03:14	slider into position and I can rotate that that'll still have that clutch piece working here and then I'll allow the coin slider to rotate in only one direction that was the theory now as far as the timing of the the grabbing and
00:03:31	dropping of the coins is concerned you can see um I I highlighted this with a black Sharpie here but you can see that the part this part here sticks out just a little bit further than the rest of the edges here so my theory was to put
00:03:47	the coin slider into position here and when it goes through these cogs you can see that it actually pushes down on that area let's see if we can find a better maybe if we do it over here on this
00:04:06	piece you can actually [Music] see you can see that when this is in that position this Cog is actually pushing down on this whole mechanism and that's how we would actually pick up a
00:04:24	coin in that position so you can see that there's a pretty big gap here right now but when I rotate that past this Cog that tightens up that means that this Gap in here has opened up enough to allow a penny to slide in there and once
00:04:40	it's through there the penny is firmly held and it can rotate into the next camera position so in that position it is just hanging out in space and you can see that on the other side like there's nothing holding the penny other than
00:04:57	this this coin sliding me ISM when it gets to the third position that would be the coin sorter position it will push down on this Cog again and then it will just drop it through that Center hole so that is how
00:05:14	that was supposed to work and I was pretty excited when I got to see this um so as far as the timing is concerned we want to make sure that we are pushing down hard enough on this Cog to pick up a penny
00:05:30	and make sure that we actually have enough space there to pick up a penny but then we want to make sure that there's enough room for it to return and positively hold on to the penny without letting go of it because of that coin
00:05:43	Studio position that I was talking about before it we don't want that to actually fall when it's in the in the camera studio position if it fell in this position it would kind of be a disaster that would fall on top of one of the
00:05:58	cameras and that would not be great so at any rate that took a lot of work to get that distance um set up properly and I actually had to go through a bunch of different iterations which you can see here on the the table basically what
00:06:13	I needed to do was to set up uh different distances from the center here to the outer edge and in this case you can see that that's 124 mm um and then and then you can also see that that's too
00:06:31	loose so that's a problem um and I can also show you what that looks like uh with with the mechanism that's too loose it when when it rolls past this Cog there's really no push there it doesn't do anything to actually hold or release
00:06:50	the penny in those positions so um obviously that's too loose and this just slides by there way too way too effortlessly and there's no no connection there um but what I did was basically just increase that amount by
00:07:05	half a millimeter each time until I got that uh that pressure correct so you can see that I stepped up to 124.5 mm you can see that we're starting to engage with those cogs but we're still not getting very much movement down here at
00:07:22	125 mm we see a little bit more engagement it's starting to close that Gap a little bit more but we're still not seeing enough but to make a long story short um you know I I stepped up
00:07:42	by half a millimeter each time and what I ended up with was 1265 mm for that distance and that seems to be just about right as we demonstrated before when we rotate that by one of the cogs there is significant
00:07:56	movement here and that opens up the Gap here so that we can actually grab onto a penny and when we don't have a cog like over the camera studio here it works pretty well because it will have room to fully disengage and it will actually
00:08:11	hold on to the penny in this position like we showed before the other problem that I ran into though was that there's a lot of friction in this system if you look at the way the Cog timings work on this you can see that two of these are
00:08:27	being pushed down at EX actly the same time so these have maximum pressure on them both at the same time and that makes this extremely difficult to turn so I knew uh that we needed to do some things to kind of loosen that up a
00:08:44	bit and the first thing I came up with was to try to change where the position of these cogs was so that they weren't pushing down at their Max deflection at exactly the same time so in the next consideration you can see that when this
00:09:01	is at Max deflection this no longer is at Max deflection that reduces the friction of that connection significantly but as I got thinking about this and as you look at this under
00:09:14	here you can now grab this more fully when you try to rotate that from here there is still a significant amount of friction it's very very difficult to turn this so that amount of friction even though we're not pushing these down
00:09:35	at the same time made me think that maybe there's a a better way to do this the one thing that I noticed about this was that a lot of these intricate parts were getting caught on the gears underneath here they were getting caught
00:09:48	under here that was making it very difficult to turn so if we pull this out one of my my ideas for reducing friction in this system was to just cover up those gears with a piece of paper temporarily just to see how that works
00:10:02	you can still still see that we have an engagement with the gears here and when I put that back in this now rotates much more easily that allowed these intricate parts to slide over those gears more easily it's still
00:10:18	pretty hard to turn from that Center post it still gets caught so I think that's just a product of trying to turn this from a very small gear here in the middle but you know I soon realized that having a such a thin part there was not
00:10:36	a long-term solution so rather than using a piece of paper I just printed this plastic a little bit better and uh I created something I'm calling a coin shelf it's just a thinner version of that part that I was showing before and
00:10:50	that incorporates what I was trying to do with the paper mask there it just allows this to roll over everything without getting caught up in the gear this should cover the gears and all those other things that I had going on
00:11:02	and that will make it a lot easier for this to rotate I think that's enough for this video but in the next video I think what we really need to discuss is a better way to turn this um as you can see it's much easier to turn this if we
00:11:19	do it from this outside edge and I think that's going to be the key uh in the next video we're going to figure out a way to attach a gear to the outside rim of this and we'll be able to turn that um from the outside edge rather than
00:11:33	trying to control it all from from this small gear here in the center so stay tuned in the next video we're going to talk about that outer gear and a way to turn this and use mechanical advantage to create more torque so I'm kind of
00:11:43	excited about that stay tuned for the next video and I'll show you how that gear and pulley Sy and is going to work thanks everyone