Another Blade Runner thread: The Portable Voight-Kampff Scanner
- Thread starter Ein
- Start date
Love every bit of info that you’ve posted. A lot flys over my head, but it’s surly interesting to read.
You’re a beast mate, keep it coming :thumbsup
You’re a beast mate, keep it coming :thumbsup
Borax
New Member
Good work Ein! Looks really well thought out.
I want to address two (minor) points:
regarding the charging rate: you'll be fine with 500mA for a 400mAh battery.
Although for that charging current you should consider making the traces on the PCB a bit thicker. It's the most current the PCB will ever see and these traces are among the thinner ones.
Do you? I worry that the device would make a small "pop" sound when the amp turns on before the teensy DAC is initialized. You should try If this happens on your setup. If not, you're fine. If it indeed does happen, you may want to spare an extra pin from the teensy to turn the amp on once it has initialized the DAC output.
The layout for the amp looks very tidy on your PCB, good job on that!
Amazing work, as always!
I want to address two (minor) points:
regarding the charging rate: you'll be fine with 500mA for a 400mAh battery.
Although for that charging current you should consider making the traces on the PCB a bit thicker. It's the most current the PCB will ever see and these traces are among the thinner ones.
Do you? I worry that the device would make a small "pop" sound when the amp turns on before the teensy DAC is initialized. You should try If this happens on your setup. If not, you're fine. If it indeed does happen, you may want to spare an extra pin from the teensy to turn the amp on once it has initialized the DAC output.
The layout for the amp looks very tidy on your PCB, good job on that!
Amazing work, as always!
Ein
Sr Member
Got a lot done over the weekend and I'll do some more write-ups when I have time, but I've been working on the sliding mechanism and trying to come up with something robust enough to survive use as a cosplay prop while not being insanely complicated to engineer and build, for my own sanity's sake.
One thing I noticed is that the back rail on the prop appears to be... well, a linear rail.
It has all the hallmarks of the larger linear rails I'm used to working with on 3D printers - mounting holes going through the length of the piece, the two side grooves. Looks pretty much like what I'd expect.
It makes sense in the context of that part, too, as I'm sure it serves as a useful guide to keep everything moving in straight lines when the slide deploys. That said, the rail part of that has to be at most like 3mm wide. I've been scouring the internet to see if I could track down a part with similar dimensions and I've been coming up a bit empty. Anyone know where to source this kind of thing, preferably not with a 6-week-shipping-wait-from-China? I feel like there has to be a mechanical-parts equivalent of what Digikey or Mouser are for electronics components. McMaster Carr is not bad, but they are ludicrously expensive.
One thing I noticed is that the back rail on the prop appears to be... well, a linear rail.
It has all the hallmarks of the larger linear rails I'm used to working with on 3D printers - mounting holes going through the length of the piece, the two side grooves. Looks pretty much like what I'd expect.
It makes sense in the context of that part, too, as I'm sure it serves as a useful guide to keep everything moving in straight lines when the slide deploys. That said, the rail part of that has to be at most like 3mm wide. I've been scouring the internet to see if I could track down a part with similar dimensions and I've been coming up a bit empty. Anyone know where to source this kind of thing, preferably not with a 6-week-shipping-wait-from-China? I feel like there has to be a mechanical-parts equivalent of what Digikey or Mouser are for electronics components. McMaster Carr is not bad, but they are ludicrously expensive.
Searched through my lunch hour and this is the closest similar linear rail I could find. It makes sense to come from a site such as Adafruit, but it is not square and is 15mm. I think you're right about the width and is closer to 3-5.0mm. Like you mentioned, I'm guessing the team acquired the track from a 3D printer or spare CNC parts. These rails are used in CNC, printing, and robotics.
https://www.adafruit.com/product/1861
https://www.adafruit.com/product/1861
Ein
Sr Member
The version of the back rail I have on my model is 3.5mm wide, but that was just me eyeballing scale per my methods in the first few posts.
It looks like 3mm rail does exist, but it's horrifyingly expensive for what it is. Probably one of those things where things get cheaper as they get smaller until a certain point, and then the price balloons again in the other direction because of how small the manufacturing actually gets.
I'm probably going to have to fake it as a linear rail and come up with my own solution. Right now I'm leaning towards a pair of springs on cylindrical rails as an option.
My concern is that unless I do two springs in this fashion, the slide might not deploy evenly or smoothly and could risk snagging. I could do one in the central position, I guess. Still working on the concept. I'd actually prefer an extension spring to compression springs for this thing, as it'd pull the slide up rather than push it, but the problem then becomes trying to mount the spring in a way where it's not going to also be in the way of the slide itself. I've measured the range of motion required for the slide from open-to-closed at around 24mm, which means I need about an inch of play in the spring, and I'd prefer a bit more than that so that it holds itself deployed with force.
Damnit, Jim, I'm a ̶d̶o̶c̶t̶o̶r̶ lawyer, not an engineer!
Edit: OK, spent a bit more time thinking about this, and I think I have a slightly better approach. I want to minimize the amount of wear on the sliding action, and I want it to deploy smoothly. Might use some bearings to guide the slide out...
Problem with this becomes how exactly to latch the design shut with the green button on the back, but I'll work something out given enough time.
It looks like 3mm rail does exist, but it's horrifyingly expensive for what it is. Probably one of those things where things get cheaper as they get smaller until a certain point, and then the price balloons again in the other direction because of how small the manufacturing actually gets.
I'm probably going to have to fake it as a linear rail and come up with my own solution. Right now I'm leaning towards a pair of springs on cylindrical rails as an option.
My concern is that unless I do two springs in this fashion, the slide might not deploy evenly or smoothly and could risk snagging. I could do one in the central position, I guess. Still working on the concept. I'd actually prefer an extension spring to compression springs for this thing, as it'd pull the slide up rather than push it, but the problem then becomes trying to mount the spring in a way where it's not going to also be in the way of the slide itself. I've measured the range of motion required for the slide from open-to-closed at around 24mm, which means I need about an inch of play in the spring, and I'd prefer a bit more than that so that it holds itself deployed with force.
Damnit, Jim, I'm a ̶d̶o̶c̶t̶o̶r̶ lawyer, not an engineer!
Edit: OK, spent a bit more time thinking about this, and I think I have a slightly better approach. I want to minimize the amount of wear on the sliding action, and I want it to deploy smoothly. Might use some bearings to guide the slide out...
Problem with this becomes how exactly to latch the design shut with the green button on the back, but I'll work something out given enough time.
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Can you design the green button to "lock" the rail? i.e. a clip-to-hole in rail. When depressing the button, the rail will slide out from the spring tension. When closed by hand, the clip within the button will snap back into the hole on the rail. Does that make sense?
propmaster2000
Sr Member
Since this is an open forum, I guess throwing out some ideas and see what sticks
Maybe use two tension springs on the sides and two metal guide rods running up the center
of two guide paths. Have a mechanical stop (with hole through) as the springs pulls up.
View attachment 780781
.
Maybe use two tension springs on the sides and two metal guide rods running up the center
of two guide paths. Have a mechanical stop (with hole through) as the springs pulls up.
View attachment 780781
.
Ein
Sr Member
Yeah, that's pretty much the idea at this point. I'm hoping the spring force will be enough to hold the slide out in the extended position without having to also latch it out. If it doesn't, I can put a second hole in the rail to make it catch and engage while out, but then you'd have to push the button to slide it closed. Alternatively, I guess I could have it stick in the extended position with small magnets, which would be enough to hand-push closed... but that starts to get even more complicated.
Since this is an open forum, I guess throwing out some ideas and see what sticks
Maybe use two tension springs on the sides and two metal guide rods running up the center
of two guide paths. Have a mechanical stop (with hole through) as the springs pulls up.
View attachment 780781
.
I like the idea of what you've got drawn here, and I'm very grateful that you took the time to illustrate this. I think there are a few issues:
- There are parts that will be on this thing that aren't modeled yet. The scanning LED isn't on the front of the rail yet, and you've got a spring right in that spot.
- If I cut a channel in for the guide rods like what you're showing, it makes those parts substantially harder to cast.
I think I've got an idea that'll work for this, but I'm going to build a test piece out of simpler shapes to print and prototype with.
My apologies if you have covered this before Ein. Do you plan to print the overall housing/case and then cast in a different material or simply print and finish each housing individually?
Such a lot of thought and effort on your part - thank you again!
Such a lot of thought and effort on your part - thank you again!
propmaster2000
Sr Member
Of course my drawing was based off yours and it does not show the LED holder so it looked as though there would be empty space available.
The upper spring mounts could be moved down to allow for the LED holder clearance.
Since your plan is to cast a part of the pop-up, having a clearance path (hole) for the rods would be an issue.
If there was an open slot cast in, then a brass tube could be laid in (glued) as the path for the rod.
Of course, just thinking out loud.
View attachment 780809
.
The upper spring mounts could be moved down to allow for the LED holder clearance.
Since your plan is to cast a part of the pop-up, having a clearance path (hole) for the rods would be an issue.
If there was an open slot cast in, then a brass tube could be laid in (glued) as the path for the rod.
Of course, just thinking out loud.
View attachment 780809
.
Ein
Sr Member
The only way to do multiple items like this at scale is to print one set of parts, finish them nicely, then make a mold of them and cast them. I haven't figured out if it makes sense to do the aluminum 'rail' parts as cast items, or via some other option. I have a laser-cutter, so I could potentially cut those parts out of acrylic or another comparable plastic. Unfortunately, nothing I have would be capable of cutting actual aluminum or metal parts out - the laser I have can only get through a few MM of plastic.
In any case, once the parts are cast there's going to be a bit of clean-up work required for each copied part, but that's nowhere near as much work as trying to print and clean up a bunch of 3D prints.
propmaster2000 SpeedRacerx You're both pretty much spot on with these ideas. Let me show you what I'm working with at the moment:
I was about to say that I wanted to keep the mechanics of the slide as simple as possible, but I realize that adding a pair of bearings is probably counter to that purpose. For what it's worth, I think they'll give me a reasonably smooth action. The idea on the right side was that I wanted to make sure the pink (back) rail connected to the rest of the rails on the inside of the body, to keep it from wobbling or potentially bending. The 'cup' shape was also to ensure that the slide stopped when it hit a maximum extension, and would hopefully help keep things lined up.
The problem I'm having is actually figuring out the latching mechanism. What SpeedRacerx drew is one a good option, for sure - there are plenty of latch designs that'd work for this - but I'm having trouble figuring out how to make sure there's positive tension on the latch to push it into the back rail. The problem with my existing design is that I basically end up having to put the latch underneath the pink rail, which requires a lot of weird lateral forces. This is a dumb design, but just an example:
I started playing around with the idea of a latch more directly in line with the button, which helps:
I think the issue is more that none of that solves how I put force on the latch itself. There needs to be something pushing that green element to the right. I've considered a bunch of options for that. A small elastic band might work, but I've seen these things wear out over time. Another option might be some kind of torsion spring. There's not a ton of room for that particular element, so whatever I end up going with needs to be reasonably space-efficient.
I'll probably revise this a little bit closer to what SpeedRacerx has designed once I figure out exactly what's going to keep the pressure on the latch.
- - - Updated - - -
Hey, if I really wanted to go nuts with it, I did actually find the sort of super small carriage rails that I assume they used on the film version. The 3mm one is only $90 for 40 mm of rail! What a steal! I'll just tack on $100 to each prop's cost, right?
I'm trying to do this as economically as I can, honestly. The custom PCBs actually save a lot of money in the long run - they mean I can buy raw components and put them together instead of buying fully-built things and trying to jam them into that space. A 2.4" TFT screen with the PCB on it (which I'd have to remove anyway) is $~10, while one without is only $~4.
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I don't recommend doing the rail with acrylic...it's pretty brittle and is not going to support much wear and tear unless supported by something else. On my replica I used several layers of engraving laminate that has a realistic steel effect surface called metalgraph, that can be cut with a CO2 laser. Ended up fairly tough and has a flexibility that acrylic doesn't. Just a thought
