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SARCTRAC Mk1 Construction

SARCNET
Published by Julie & Joe in SARCTRAC Mk1 · 24 August 2019
The purpose of this Forum is to help readers with SARCTRAC construction issues; to publish the user's experience and ideas; and to provide hints, tips and solutions.
We will review all posts; encourage discussion and suggestions; provide our input; and gather new material for updates of the SARCTRAC manual.

List of known SARCTRAC setup hints, tips, issues and their solutions:
  1. If you think you are missing any small parts, first have a look to see if they are hiding inside the thick heatshrink tubing.
  2. CAUTION: Don't forget to mount the 0.22uF tantalum capacitors on the voltage regulators before powering up.  
  3. Trimming the wires, from the USB Hub Hat to the components on the Heatsink Assembly, to length prior to soldering looks nicer.
  4. Due to existing slack in the motor bearings the washers used to offset the chamfer of the enclosure may not be required. Check: When mounted to the tripod with the antenna attched the vertical faces of the rotator should be vertical.
  5. Don't use steel screws to mount the 3D sensor.



13
reviews

Darrell
12 Oct 2019
I have just started construction, and note the directions and diagrams have some differences, as to the color of wires and placement. Also, I thought the GPS was not enclosed, because the photos show a different type, which must be an older model. The GPS and US Hub Hat do not fit in the box supplied, even with some modification. Also, there is no opening for the Yaesu cable. It seem like nobody has assembled the kit using the material being sent out. I have downloaded the 3d printed version, however I found out is for a serial cable, and the one I purchased is for USB. I am in the process of modifying the 3D printed version and if successful will share it. Hopefully everything will work if I can get it finished.
Julie and Joe
12 Oct 2019
Hi Darrell,
Please ensure you are using the latest version of the manual. Can you be more specific? According to the instructions you have to prise off the case of GPS for it to fit into the enclosure. Please don't forget the tape. The Yaesu cable plugs into one of the side connectors on the Hub Hat when it is finished. The schematic shows it plugged into one of the end connectors, for clarity. It is a hub, of course, so it doesn't matter. Over 30 readers have successfully completed our kit. The 3D printed version was kindly uploaded by a reader. Please let us know if using a 3D printed enclosure is any easier.
Kind Regards, Julie and Joe.
Patrick Joseph
20 Apr 2020
I would suggest that you mention to solder wires to the buzzer, and mount it to the inside of the case before the other items are mounted to the inside of the case. Mounting the buzzer using silicone is difficult when the wires from the RP0I are already attached to it, and when the inside of the case is crowded. Also, when you are doing the modification to the alternate motor driver, you also need two extra metal M3 hex nuts. The list of items needed on the modification instructions does not include these nuts.
Julie and Joe
21 Apr 2020
Hi Patrick,
Thanks for the feedback. I guess we were lucky with the buzzer. It had to be secured to the enclosure, aligned accurately with the hole in the enclosure with the glue prevented from entering the buzzer or the enclosure hole. By chance, the shank of a 2mm drill bit fitted tightly in the buzzer hole and it also fitted tightly in the 2mm hole drilled in the enclosure. So all we had to do was pre-assemble the buzzer on the drill bit, pushed through the enclosure, squeeze in the silicone and then pull the buzzer flush with the inside of the enclosure. However, this technique probably wouldn't work so well if the drill bit was loose. The enclosure is polycarbonate and the buzzer is PVA. So selecting the right glue was tricky. Maybe using a tacky glue and letting it partly cure on each surface before pressing the two parts together would be a better plan. You are right, the metal M3 nuts are missing from the parts list. We will fix that.
Kind Regards, Julie and Joe.
Trent Trent
22 Apr 2020
I just went through the manual again of the kit and I thought I would check out the jaycar tripod and well whats listed in the manual has changed
Like everything else jaycar does these days they discontinue the good stuff but the tripod they are using now is this
https://www.jaycar.com.au/large-pa-speaker-stand/p/CS2493
Julie and Joe
22 Apr 2020
Hi Trent,
While we have not ventured out to check the new tripod, it does look very similar to the original and will probably do the job. As always, Trent, you have to shop around for the right stuff and also the best deal. If you search for "Heavy Duty Speaker Tripod" images on Google, you will find many other sources for the original tripod, which by the way has 35mm tubing, two locking screws (one above the tripod hinge, not through it) and a locking pin on a lanyard. So, good luck with your search and stay safe.
Kind regards, Julie and Joe.
Alton
17 Aug 2020
Couple questions maybe someone can help.
.22 uf or 22 uf? Did not have that question till I read the first post.
Can someone give me a source for enclosure state side? I have found some close, but not exact.

Alton
N4IDH
Julie and Joe
17 Aug 2020
Hi Alton,
We use a 22uF 16V Tantalum capacitor in a 3528B SMD package. A datasheet for the regulator is here: https://www.ti.com/product/LM2940-N. The capacitor is essential as regulator instability can cause damage to the RPi0.

A datasheet for the enclosure is here: https://download.altronics.com.au/files/datasheets_H0304.pdf. In the USA the Ritec RP1135 ROHS enclosure is sold by Hammond here: http://www.hammondmfg.com/RP_ABS.htm. You could check their vendors list.

Good luck and stay safe.
Kind regards,
Julie and Joe.
Bob
02 Sep 2020
Hi folks, I am finally getting started with my kit. Working on the case holes etc. One thing that confuses me is Figure 26. It appears as if one of the case 'halves' is upside down. If I were to simply close the lid in the orientation as shown I would think the motor shafts would not be lined up. Figure 27 does seem to show the correct orientation. Perhaps I am just not seeing this right but it just appears if the motor in the lid is upside down. Am I just not seeing it correctly? Or worse not explaining it clearly?

73,

Bob WA9NBU
Julie and Joe
02 Sep 2020
That's right Bob. The wires are too short to show it the logical way around, sitting on the bench. You have to turn the cover 180 degrees as you assemble it. It is a tight fit, though, with only 1mm gap between motors. Good luck with it.
73, Julie and Joe
Bob Massey
02 Sep 2020
Thanks Julie and Joe. That explains it. Will proceed. Looking forward to getting it up and running...

73, Bob WA9NBU
Marty
22 Nov 2020
Question about the regulator heatsink MK1. You upgraded the heatsink bigger I see and moved outside of the case on the MK2. Would this be better if I upgraded my to be external?
Julie and Joe
22 Nov 2020
Hi Marty,
The SARCTRAC Mk1 kit uses a RPi0. It does have the biggest heatsink we could fit inside the enclosure, but it does get hot (50 degrees Celsius). It works OK, but you can provide your own bigger heatsink if you like. The SARCTRAC Mk2 product uses a RPi3B+ an requires a much bigger heatsink. Why does SARCTRAC require a heatsink? Read about that here: https://www.sarcnet.org/sarctrac.html#DesignNotes.
Kind regards, Julie and Joe.
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