Constructing Janus, by Dirk

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Starting Electrical layout

Postby dirktheeng » Sun May 29, 2011 2:53 am

Went out to lowes and radio shack today and spent some time with my wife... good times... also got to do a little bit of work on the laser and have some fun.

Here's a couple pictures of what I got done.

Top View

I mounted the power supply and got the wiring done to the buss. I decided to go patriotic with the wiring... red, white, and blue.... well not particularly, it was the only solid core, 14 AWG wiring that lowes had when I was there other than buying the romex and splitting out the conductors. I still wouldn't have had green for ground, but that's ok. I kind of like it... the only thing to remember is blue is black and red is green and besides, the color of the insulator doesn't affect the conductivity of the wire. :P

Here's another view.

Front view

I decided to put an upper deck above the electronics module to set the laser power supply on. I baught a piece of sheet metal at lowes for this. I will buy another length of T-strut from Misumi to support the other side on my next order along with some more corner brakcets and post-assembly nuts.

I made the power cord for the board out of 22 AWG stranded wire and twisted them together with a drill. The center post is positive as per the instructions. I wrapped the conductors in nylon webbing and heat shrinked the ends. I think it looks really nice.

Tomorrow, I will tackle running the wires for the motors.
Last edited by dirktheeng on Tue May 31, 2011 1:31 am, edited 1 time in total.
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Running wires

Postby dirktheeng » Mon May 30, 2011 7:42 pm

Well, I am just about done running the wiring.

The first thing I did was solder on the wires for the X axis limit switch. To get extra clearance on the Y axis, I flipped this to the other side (just in case you are wondering. I ran the wire accross the gantry in the rear underside slot. For now, I just taped it in with masking tape, but will put a slot cover on later when I make my next order to misumi. The wires are twisted pair wires I made from 22 AWG connector wire I had from Radio Shack. I chuck them in an electric drill and carefully controll the angle of the wires to the twist point and tension with my hands. I can usually get them to twist at about 6-8 twists per inch. This should help reject noise coming onto the board. I wrapped the wires in nylon cable sheith and heat shrinked the ends. This made the cable easier to run and looked very nice.

X axis limit Switch

The next thing I did was connect up the Y axis limit switch and run the pair of wires through the cable carrier. I should mention also that the nylon cable sheith adds significant diameter to the wire, but 2 limit switch wires could be stacked vertically in the cable carrier raceway. Even without the sheith, there one couldn't fit 3 on top of eachother.

Y axis limit switch

You can also see the masking tape holding in the X axis limit switch cable.

The next thing I did was connect the 4 conductor wire to the X axis motor. I split the cable sheith back about 6 inches so I could get heat shrink on each wire. I cut the wires and connected them on 1 inch intervals so that I wouldn't increase the diameter much at one spot. Once soldered and insulated, I was able to push the whole thing back into the cut cable shieth and then I put the nylon webbing over the whole cable and fed it through the cable carrier. I found a neat way to run the wiring with an adhesive backed cable tie mount. I put it on the metal plate that holds the motor mount screws. I cut the corners out to make it fit well. It keeps the cable secure and does not let it move when the gantry moves. I would reccomend that people run their cables this way. It also keeps the cable off the v-rail.

Here's a pic showing the the wiring running to the motor. You can see some of the colored wires showing through the split shieth.

X axis motor wiring

I ran the cable this way because my gantry arrangement allows the Y axis car to move all the way over and contact the side plate that the motor is mounted on, so I couldn't let wires or tubing sit there or I would loose usable gantry space.

X axis wire mount

Here's a pic showing the way I ran the cable and the tubing into the Y axis cable carrier.

Y axis cable arrangement

Here''s a view of the exit. You can see the tubing coming out with the rout to the rear, the motor cable, and the 2 limit switch wires. I fed them into 1 cable nylon cable shieth and then bound that witht he cover safety switch line and ran that to the driver board.

Y axis cable carrier exit

I tell you what, the hardest thing so far has been running the tygon tubing through the Y axis cable carrier. This raceway has to be shared by a 4 conductor motor wire and 2 sets of limit switch wires. It was really difficult to get the tube run after I got the wires installed. I tried about 5 times before getting it right. The tygon tubing just barely fits in my raceway with the other wires, so it was a tight squeeze to begin with. To make matters worse, the tubing is very "grippy" (it has a high friction surface and doesn't slide along anything well). I used an old piece of cat 6 cable I had around to feed through and use as a pull wire. I tried taping it off with masking tape to connect the tubing and wire. The first try, I only got about 2 inches in b/4 the tape broke. Then I tried the saliva lubrication, maybe 8 inches. Then I tried lubing the raceway up with hand soap by draging the cable back and forth and putting soap on it... about 10 inches. Then I tried feeding it and lubricating the tubing as it went in, about 2 inches from almost all the way and I actually broke the shieth of the cable I was yanking on!! Finally, i used duct tape and lots of soap on the tubing and I got it through! The duct tape came off the cable after it made it through about 3 inches. I was able to use a pliers to pull the tubing through. If I were to do this over again, I would use a wider cable carrier and/or maybe not put cable sheith on everything. Anyhow, I didn't break the tubing and it's in with the wires run as well. The tubing still caries air through it so I am calling this a big success.

Here's a view of the mounted driver board with room to spare. I will put the arduino's in the space to the left of the driver board. The X/Y limit switches come accross the mouning board vertically and meet up with the cover safety switch which runs horizontally accross the botom of the pic. The safety switch wire follows the extrusions to the lower, right, front corder of the machine. The soldering looks the same except the red wire is connected to the normally open side of the switch.

Wire routing to driver board

The Pololu driver board was mounted by attaching PC stand offs I got at Radio Shack to the board, marking the spot and gluing them down with super glue. I markde the spot where the stand offs were when the board was aligned, then I puddled a little super glue and put the board in place. The spacers are M3. I didn't have any long enough and I didn't feel like going to buy some somewhere. The glue method worked well and I didn't have to worry about drilling holes in the right spot. You can also see a scrap piece of twisted pair wire I made.

Pololu driver board mount

One other change I'm going to make is getting a right angle barb fitting and routing the hose as shown here so it doesn't interfere with gantry motion.

nozzle change

I'm also going to have to tap the fitting a little deeper. As is, I can only get a few threads in by hand and there is a lot more room to get the fitting in deeper.
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Finished motion control wiring

Postby dirktheeng » Wed Jun 01, 2011 3:07 am

I finished up the wiring for the motors which completes the motion control wiring. Here's some pics of the finished stuff:

Z axis go the same treatment as the X axis and is run in the forward slot of the rear bracket.

Z axis motor

Oh, I forgot to mention that I drilled 4 holes in the botom skin to let me have access to the Z axis motor screws when I need to.

The X axis is wrapped the same way and run down the strut and through the adjoining horizontal member. Currently held in by masking tape (wonderful stuff) but will be replaced by slot covers with my next order. Also, the threaded rod shafts and couplings will be going and be replaced with lengths of the precision shaft I have and new couplings that I will get from misumi. This may be the last time they show up on my project pics.

X axis motor

And the wires are run and connected to the driver board.

Driver Board Connections

That's all for now... next up: getting the arduino's installed and brining this thing to life. The Arduino's should be here on the 2nd (I hope).
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Re: Constructing Janus, by Dirk

Postby tylerv » Wed Jun 01, 2011 4:47 am

You laser looks really good so far! I'm excited to see how the Arduinos work when you get them installed. I may pick your brain when you get them up and running...

BTW, I used your idler bearing assembly mod when I installed the belts in my laser. The sanded metal rod works really well. I just got a normal 1/4" rod (vs. high precision rod), but it works lots smoother than the 1/4" machine screw that was in there previously. (Bart, I second putting this or something similar the design).
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Location: Utah, USA

Tested the driver board

Postby dirktheeng » Fri Jun 03, 2011 1:08 am

Well... I got my power chord from storage today so I was able to power up the board. At first I was a little scared because the fan wouldn't turn. After I powered it down and back on it worked fine. I have not been able to repeat the behavior since, so I'm not too worried about it and it seems to work fine now.

I connected a 5 vold wire to the motor enable/disable pin and the motors locked up and I was not able to move them. I suppose that means it works just fine. I am very excited about that.
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Power supply for arduino's????

Postby dirktheeng » Fri Jun 03, 2011 1:35 am


I need to figure out a power supply for the arduino's. The documentation reccommends 7-12 volts, but doesn't say how much current they need. Does anybody know how much they could expect to draw? I am running one Uno and one Mega. Also, can anybody suggest a cheap solution for either powering it off AC or the 24 V power supply?
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Re: Constructing Janus, by Dirk

Postby BenJackson » Fri Jun 03, 2011 1:53 am

Some nominal amount of current like a few hundred mA.

Find the power supply chip on the board (or just link to where you bought it so we can find the schematic). Then google the datasheet and see what its max voltage is. It might take 24V as-is. If not there are various solutions which we can recommend for the specific board.
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Re: Power supply for arduino's????

Postby FunGizmos » Fri Jun 03, 2011 5:18 am

I sell these 9v wall adapters ... cts_id=183, or you can find many 5v regulated supplies on Ebay something similar to: ... 2a02552fd4 which you could mount easier inside on your power skid.

The should have no problem running both of your Arduino's off a 1amp supply. If you use a 5v regulated supply you hook it directly to the 5v rail of the Arduino bypassing the on board regulator (Just double check and ensure your supply is supplying 5v first.)

The Arduino is rated for 20v Max suply but you you really don't want to use anything higher then 12v, doing so will just make the Arduino's on-board regulator run super hot.


I need to figure out a power supply for the arduino's. The documentation reccommends 7-12 volts, but doesn't say how much current they need. Does anybody know how much they could expect to draw? I am running one Uno and one Mega. Also, can anybody suggest a cheap solution for either powering it off AC or the 24 V power supply?[/quote]
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Re: Constructing Janus, by Dirk

Postby naPS » Fri Jun 03, 2011 5:57 am

I blew up a MEGA running 12v. I think the regulators on them can't handle much. You can power them off of any USB adaptor, there's tons of them. Phone chargers work really well for them.
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Power Supply for Arduino's

Postby dirktheeng » Sat Jun 04, 2011 2:22 pm


I think I found what I need for powering my little friends. I found the PSU on ebay ( ... 3a52eed2f2). It will accept ac (transformed down to 22v or less) and DC from 4-30V. It will output between 4.5 and 30V, regulated DC up to 1.5A. Best of all it's only $10 with shipping and it is assembled! Here are a couple pics.

PSU module

Wiring Diagram

I'll probably set it to 9V or so
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