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Drone kit -Building a Tarot Mini 250 (TL250A)

Preamble

I got hold of a clone of the Tarot Mini 250 through the machine frame TL250A, and this is my build log. See also Drone kit -ZMR 250.

The first questions that immediately came to mind were:

  • Where can I download the assembly manual?
  • Which size hex screwdriver is required?

Please note that this is an on-going blog, and things will change from day to day, as extra information is added, and errors are retrospectively corrected. Please bear that in mind, when reading this – This is not a finished blog, as yet, by any means.

The featured image shows the wiring schematic for a TL250A with a Naze32 v.5, from the youtube video, Tarot 250 (TAROT TL250A) setup with naze32 & futaba subs. However, in this build I am using a CC3D, as the manual/user guide intends.

Useful links

Trying to locate an online manual

There doesn’t appear to be a PDF of the assembly guide readily available online.

Don’t download the 250-280 Through kit Manual, which comes as a RAR file, it is the wrong manual.

The promisingly named Tarot 250 project – step by step build was not terribly useful

This thread seems quite helpful, Building The Tarot TL250A Mini FPV Frame.

I got a message back from the seller:

Pretty sure Allen wrench is 1.5mm.
Frame didn’t come with any instructions, so I used a combination of YouTube videos, such as Tarot 250 mini quadcopter build and review and Google images. As you can probably see the solder pads were not very well marked so would suggest using a continuity tester just to confirm what goes where.
There are lots of wiring schematics on Google images.

After three days, I finally managed to find a manual! It was buried in a thread on rcgroups, TAROT Mini 250 Quad Kit TL250A – Link: PDF: tarot-mini-250-300-quad-assembly-instructions.

The PDB

The PDB really is a work of art.

The Tarot TL250A PDB
The Tarot TL250A PDB

Screwdriver set

Cheapest seems to be an allen key set: 7PCS 0.7mm-3mm Mini Hexagon Hex Allen Key Wrench Screwdriver Set Tool Kit, £1.80, or 7PCS Micro Mini Hex Wrench 0.7mm-3mm Alloy steel Set Tool Kit DIY Screwdriver, £1.19. Note that the 4 and 5mm keys are not included:

Hex key table
Hex key table

If I get the complete set then I can empirically see which key fits the screws in the Tarot 250 kit.

The cheapest set of actual screwdrivers seems to be 6Pc HEX Precision Screwdriver Allen Key – Sizes: 1.5mm 2mm 2.5mm 3mm 3.5mm 4mm, £5.49, but does not have the 0.7 mm, 0.9 mm nor the 1.3 mm hex heads, but does have the 3.5 mm and 4 mm heads.

I ended up using a T6 torx!

Tips

Top tip: Assemble the kit, before you solder the electronics on to the PDB. Do this is stages, i.e. the top part first, and then add the PDB afterwards. Even though it may seem that you are undoing and then redoing  parts of the kit, it doesn’t matter – time is on your side. It is better to see how each part goes together seperately rather than trying to do it all in one go.

First, put the straight body part on to the landing gear, it just clips on.

Then place the two arms and the two braces on first and screw them in, with one long black screw as the center screw and two long silver screws on each side, of the braces. Do this before the PDB goes on, just to get a feel for the assembly.

Then unscrew the four silver screws, leaving the black ones in place.

Squeeze the legs of the landing gear slightly at the rear so that they can slide into the grooves at the back of the PDB.

Ensure that the screw holes of the PDB, landing gear, the two arm plates and the braces line up and then put the four silver screws back in.

When screwing, do it slowly, to ensure that the arm and/or braces are not being warped, and that the screws are going in true.

Parts List

  • Carbon Fiber Front arm set
  • Carbon Fiber Rear Arm Set
  • Carbon Fiber backbone
  • PDB
  • 40 mm x 40 mm Carbon Fiber FPV mounting plate
  • Landing skids
  • 1 x fore metal brace 730 mm
  • 2 x metal body braces 485 mm
  • 2 x 12mm long black M2 bolts
  • 10 x 14mm long silver M2 bolts (I only had 8)
  • 6 x M2 nuts (I only had 4)
  • 12 x M2 washers (maybe more, 18? I only had 11 supplied)
  • 7 x 4mm M2 small black bolts
  • 6 x 6 mm Hex M2 spacers (I only had 4)

NOTE: En lieu of the 6 x 6 mm Hex M2 spacers, 6 x M2 nuts and 6 x 14 mm M2 bolts, the original comes with 6 x 6 mm nylon clip-in spacers.

Sourcing the missing parts

Hex spacer
  • 6 mm high
  • 4 mm wide
  • M2 (2 mm) diameter

M2 Black Nylon Hex Female-Female Standoff Spacer, Hexagonal

10 @ £1.30
100 @ £6.90

Bolts

M1.4-M2 M3 304(A2) STAINLESS STEEL ALLEN BOLT SOCKET CAP SCREWS HEX HEAD QTY-10
M2 x 14 mm
10 @ £1.01

Half nuts

M2 / 2mm STAINLESS STEEL A2 HEXAGON HALF / LOCK / THIN NUTS FOR BOLTS SCREWS
M2
10 @ £0.99

Washers

A2 Stainless Steel Form A Flat Wshers to Fit metric Bolts & Screws M1.6 to M30
20 @ £0.99

Note that these washers are 0.5 mm thick, which are too thick, and hence would be adding unnecessary weight. The washers that came with the frame are wafer thin. Thinner than 0.3mm even, such as A2 Stainless Steel Form Flat Washers M5 M6 M8 M10 M12 Thin Type Washers X100pcs, for £1.16. However, 0.3 mm does appear to be the standard, see Wikipedia – Washers, unless the included washers are shims, or gaskets.

Assembly Steps

As an online guide to construction does not exist, and it does not seem possible to download a PDF of the supplied assembly instructions, here is a pictorial step by step guide:

NOTE: The three metal braces are threaded, and all bolts screw into the braces.

NOTE: Blue (not red) loctite thread lock should be used on all bolts and screws, as vibrations caused by the motors can cause the bolts to come loose.

1 – Screw in the fore metal brace to the front of the main backbone with one small black screw. Mine was already screwed together, yours may not be.

2016-10-08-3051foremetalbracecrop

2 – Clip the main backbone on to the landing gear. It is quite tight, so you may need to bend the legs together slightly in order to spread the flanges in the top, between which the backbone clips into.

2016-10-08-3050backbonecrop

3 – Place the front arms and screw on the front metal body brace, with only a long black center bolt.

4 – Place the rear arms and screw on the rear metal body brace, with only a long black center bolt.

5 – Screw the front arm plate to the fore metal brace with two small black screws.

2016-10-08-3042forebracefrontarmcrop

6 – Bend the rear legs in slightly and clip in the PDB.

2016-10-08-3041legsqueezecrop.jpg

7 – Screw in the four long silver bolts through the PDB into the front and rear metal body braces. Use washers to protect the PDB from damage from the screws.

8 – Screw the PDB into the fore metal brace with two small black screws. Use washers to protect the PDB from damage from the screws.

2016-10-08-3024forebracecrop

9 – Attach the front mounted FPV camera mount with two small black screws.

10 – Using the black hexagonal spacers between the PDB and rear arm plate, screw the rear of the rear arm plate to the PDB together using the long silver screws. Use a nut to secure. Use washers on both top and bottom, to protect the PDB and the carbon fibre top plate from damage caused by the bolt and nut.

2016-10-08-3027reararmrearspacer2crop

11 – Using the black hexagonal spacers between the PDB and rear arm plate, screw the front of the rear arm plate to the PDB together using the long silver screws. Use a nut to secure. Use washers on both top and bottom, to protect the PDB and the carbon fibre top plate from damage caused by the bolt and nut.

12 – Using the black hexagonal spacers between the PDB and front arm plate, screw the rear of the front arm plate to the PDB together using the long silver screws, on both the left and right hand sides. Use a nut to secure each bolt. Use washers on both top and bottom, to protect the PDB and the carbon fibre top plate from damage caused by the bolt and nut. I found that I was missing the two required spacers, as I only had four, and not six, so this may be optional.

In fact the original TL250A from Tarot has white plastic spacers (six in total) for steps 10, 11 and 12, as seen circled in red in these images:

However, the clones may only come with bolts, nuts and nylon hex spacers. In addition, not all of the clones have the forward spacers as shown in step 12.

Soldering on header pins

I added three strips of four header pins (black, red and white) to the underside of the ESC control mounts which go to the flight controller.

ESC control header pins, taken from underneath
ESC control header pins, taken from underneath

Arguably, the wires/connections should go to the top side, which is nearer to the flight controller (assuming that it is mounted on the top of the quadcopter. However, if using header pins, then there is not sufficient clearance for pins (signal and V+ of M4), as the top front motor mount plate obstructs access slightly.

Lack of clearance, taken from the top
Lack of clearance, taken from the top

I soldered on a strip of four right angle header pins, for the VTx (should be GPS, to the rear? 5V, GND and Rx – the fourth pin, which, I presume, is intended for the GPS Tx pin, is not routed to the rear)

[photo of 4 pin right angle header pins]

The pin mapping of the four pin header is as follows (left to right, looking at top side of board):

  1. GND to GPS;
  2. 5V to GPS;
  3. Rx to GPS;
  4. n/c to GPS.

I soldered on a strip of ten right angled header pins, three of which are for the GPS (should be VTx to the front? )

[photo of 10 pin right angle header pins]

The pin mapping of the ten pin header is as follows (left to right, looking at top side of board):

  1. Vin to OSD;
  2. GND to OSD;
  3. A/V to OSD;
  4. GND
  5. V+ (confusingly labelled 12V in the PDF, but goes to 5V camera voltage supply (without a regulator/BEC)
  6. A/V in from camera
  7. GND (?)
  8. V – 12V
  9. ?
  10. ?

Motors

I considered getting a set of 1804 motors, from ebay, NEW 4pcs NEW Brushless Motor 1804 KV2400 CCW CW for 220 240 RC Mini Quadcopter E, for £16.81, by they came with no screws, and so I need to confirm the screw size. Finding a technical drawing from RCX ZMR 1804 2400KV Micro Size Integration Outrunner Brushless Motor:

So, I purchased 4 x 1806 2280KV Motors + 1 x SP Racing F3 Acro for FPV Racing Quadcopter Drone for £25.50, which came with M2 screws, and a spare flight controller. When they arrived, I found that they fitted perfectly. I mounted them upon the arms.

Initial thoughts

This is an excellent kit, I would say better than the ZMR250 for its tight design and overall looks. I particularly like the integrated PDB.

However, if an arm breaks then it would be necessary to replace both arms, as the front left and right arms, and rear left and right arms come as two plates, one for the front set and one for the rear set.

Specifications

Taken from the product website

Product parameters

  • Wheelbase: 250MM
  • Empty rack height / assembly height: 43MM / 85.8MM
  • Empty frame length / assembly Length: 195MM / 288MM
  • Empty frame width / assembly width: 219MM / 315MM
  • Bottom headroom: 21.8MM
  • Empty weight / takeoff weight: 115G / 430G (including 2200MHA battery)

Product Specifications:

  • 2.0 pure carbon plate × 1 (159 × 33 × 2.0MM) 11.7G
  • 2.0 Front pure carbon plate × 1 (219 × 49 × 2.0MM) 16.5G
  • 2.0 After the pure carbon plate × 1 (219 × 58 × 2.0MM) 16.9G
  • 1.0 before the legislature of pure carbon plate × 1 (159 × 33 × 2.0MM) 1.3G
  • PCB circuit board × 1 (181 × 106 × 19.5MM) 28G
  • Plastic Tripod × 1 (175 × 108 × 43MM) 25G
  • Before metal supports × 1 (73 × 10 × 8MM) 5G
  • Within M2 × 4MM round head Allen screws 0.2G × 7
  • The metal support frame × 2 (48.5 × 4 × 8MM) 1.7G
  • M2 × 12MM hex head screw cup 0.3G × 6
  • Flight Control sided adhesive × 1 (35 × 35 × 1.5MM) 0.5G
  • Ties battery × 1
  • English manual × 1
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