Aurdino Mega TCB

[Captain Morgan]

I also think that I should share my experience.

If anyone needs more information on my version of the TCB board, I'm ready to share it with the community.

[baldrick131]

That would be a good idea and I'm certain it would be helpful to others looking to build their own TCB

[LukeZ]

Thanks for the SBUS tips, but I plan to add inverted input so any SBUS receiver can be used.

I understand its just a simple inversion...

So I would be looking to do something like this but with surface mount like BC337 I think is OK, the light controller tested my limits of eyesight and co-ordination, fortuantly I have a friend who is an electronics whizz who has built a hot plate with temprature control I could use, and when combined with JLPCB mask the reflow went OK - but I am not in a hurry to repeat a project with surface mount!

In fact you can make the inversion circuit with a through-hole component, no need to do surface mount. Almost any run of the mill NPN transistor will work, such as the 2N2222, 2N3904, BC337, etc... Here is a sample schematic, and I don't believe the resistor values are all that critical either:

ezgif-3-c198b26e38.jpg (11.35 KiB) Viewed 3270 times

About the serial motor output, do many people use that? Here in UK even the 5A is £55 or more, if you went Deluxe with 2* Hobbywing 1060 they are £20 each so £40 total. The Sabertooth I guess makes sense in a small tank but I am rebuilding a HL Tiger 1 and it seems there is plenty of space inside for ESC and a TCB board of some find (using Taigen chassis, so no large HL battery box to deal with).

I think most people actually just use standard ESCs as you are planning to, and those will work just fine. The advantages to the dual motor controllers as you say are the smaller overall size, and also, they usually involve far less wiring since you don't have to provide power lines and signal wires to two individual speed controllers. Another advantage is that they operate at higher frequencies than most cheap hobby ESCs, so you don't have that annoying motor whine at slow speeds. However these advantages as you point out come with a significantly higher price tag, so for most it isn't worth it.

When designing my version of TCB, I made control signal outputs on the board that go to the L298 chip in order to connect the VNH2SP30 driver (more precisely, its clone with Ali), for use as tank movement motor drivers.

I have tested this very idea with the AliExpress drivers that you describe, and it does indeed work fine. As you say, the Chinese are not known for quality and I think their chips are sometimes counterfeit or maybe factory rejects, so that can be a problem. But for how cheap they are to purchase it can be worth a test.

I had to assimilate a lot of knowledge.

I'm sure that's probably the understatement of the century!

This might seem a silly question but with Hobby king messing up production of the board and people having to make their own would it not be possible to use the adafruit motor shield plugged into the top of the mega to drive some motors and servos?

Not a silly question, but unfortunately no it will not work. The problem is that the Adafruit (and other brand) motor shields do not use the same pins that the TCB does, and the pins it does use we need for other purposes. So although the hardware on those shields is perfectly good they are not wired in such a way that they can be easily adapted.

[whitecitadel]

Nice to see some posts on this thread and by what appears to be more technically minded folk than me.
...
As you can see my set up meant space is limited so I knew the small board was my only option and the 2 ESCs enabled me to put them between the gear boxes.

I can see now why you were focused on small, the Tiger 1 has some more space so for now I am looking to build something easier, larger (and cheaper!) as first attempt.

If suddenly anyone is interested in the scheme, then it is located
True, I cannot vouch that I did everything perfectly, I have no education in the field of electronics.

Thanks, I had seen your board somewhere (probably the OP forum) as I remember the colourful servo headers and made a note that was a good idea! Thanks for sharing your file I am taking a look to see what I can learn. How is assembly for your board, looks like you went into production, was it OK to get the SMD components soldered?

In fact you can make the inversion circuit with a through-hole component, no need to do surface mount. Almost any run of the mill NPN transistor will work, such as the 2N2222, 2N3904, BC337, etc...

Thanks I realised that and read (more than once) the entire thread on the OP forum on the generic Mega board and I think its also covered a few times there. I am going to order up some components and I think experiment on a breadboard to make sure I really understand everything as first step - BC337 I had in the basket (very cheap!) but will look at the 2N2222 as well.

I think most people actually just use standard ESCs as you are planning to, and those will work just fine. The advantages to the dual motor controllers as you say are the smaller overall size, and also, they usually involve far less wiring since you don't have to provide power lines and signal wires to two individual speed controllers. Another advantage is that they operate at higher frequencies than most cheap hobby ESCs, so you don't have that annoying motor whine at slow speeds. However these advantages as you point out come with a significantly higher price tag, so for most it isn't worth it.

I think for first attempt I am going to stick with ESC, it makes the board simpler and there is enough to learn and oppertunity to make mistakes with design without that complexity.

I am considering having a small PCB that has a row of XT60 to take battery in, then out to two ESC plus some smaller (JR or JSC?) plugs for the TCB and anything else that needs power like UBEC to servo's and can avoid the TCB PCB.
I did some reading on the cannon smoke on the OP forum with the 5v relays, that seemed another good candidate to power direct from battery supply (assumung smoker takes 7.4 not limited to 6v).
The advantage of such a board is that it would be useful in crawlers, boats etc and so it would be worth the investment in 10-20 PCB and they would not be very big so not to expensive. Need to do the math on current capacity, but two big planes 50% each and mount connectors in a row should be simple enough - in theory...

Lots of ideas to have fun with at least. Ordering some resistors and transistors to play breadboard POC as the next step for me - while starting to experiment with EasyEDA for later.

[Captain Morgan]

If suddenly anyone is interested in the scheme, then it is located
True, I cannot vouch that I did everything perfectly, I have no education in the field of electronics.

Thanks, I had seen your board somewhere (probably the OP forum) as I remember the colourful servo headers and made a note that was a good idea! Thanks for sharing your file I am taking a look to see what I can learn. How is assembly for your board, looks like you went into production, was it OK to get the SMD components soldered?

When ordering printed circuit boards (jlcpcb), I ordered a stencil for applying solder paste.
Next, I designed a frame for the stencil and printed it on a 3D printer.





This is the very first version of my TCB design, greatly reduced in functionality (mosfet was removed, and then I had little understanding of the TCB project device, for example, I did not understand the difference between pin arduino and pin atmega 2560 at all).

I soldered after I put the parts in place with tweezers, I put the board on the 3D printer table, heated to 100 degrees Celsius, and melted the solder with a soldering dryer.

[whitecitadel]

Ah it was you with the “amazing 3D printed paste screen book” as I called it!

That really is a work of art, when I did my only SMD project I used spare boards around and a sticky tape hinge for the jlpcb screen - very low tech but it worked!

There is certainly a steep learning cliff, I have been staring at schematics and BOM’s for several days and it is now finally making some sense. As you say it’s very confusing to link together:

• AT mega PIN number
• Arduino PIN number
• D6, A5 etc
• PK3, RXLED, etc

The pdf Luke posted is helpful, but when you look at peoples designs with the atmega “pro”, then the original OP TCB and then circuit diagrams - it does make your head hurt!

I think I have a list of most common components ready to buy, I will try practical experiments in a breadboard to make sure I understood before I try to draw any circuits, it’s also tempting the more you learn the more you want to try and add to the board!

Edit oh and tip for jlpcb, if you order the screen it defaults to quite a large dimension, is it 200*200? You can change the paste screen dimension, for the small rc light controller on GitHub I made I just shrunk the screen to be a few cm larger than the pcb in each dimension - it made the postage cheaper too!

[LukeZ]

I am considering having a small PCB that has a row of XT60 to take battery in, then out to two ESC plus some smaller (JR or JSC?) plugs for the TCB and anything else that needs power like UBEC to servo's and can avoid the TCB PCB.
I did some reading on the cannon smoke on the OP forum with the 5v relays, that seemed another good candidate to power direct from battery supply (assumung smoker takes 7.4 not limited to 6v).
The advantage of such a board is that it would be useful in crawlers, boats etc and so it would be worth the investment in 10-20 PCB and they would not be very big so not to expensive. Need to do the math on current capacity, but two big planes 50% each and mount connectors in a row should be simple enough - in theory...

You might find it interesting to know that you can get XT60 and the smaller XT30 in PCB format for easy soldering directly to a circuit board. Just Google "Amass XT60 (or XT30) PCB", you will find them for sale on AliExpress, Amazon and elsewhere. Here are some pictures:

XT60_PCb.jpg (23.33 KiB) Viewed 3235 times

XT30_PCB.jpg (26.82 KiB) Viewed 3235 times

The XT30s are probably more than adequate for most RC tanks and would take up less space.

I agree for such a board copper planes are the way to go instead of traces. Rather than do 50% each, just make the top of the board a single plane and the bottom of the board another plane, that way you can use the entire surface area for both positive and negative. Some fab houses will sell boards with thicker copper (2/3oz instead of 1oz) which can help with current-carrying capacity. Also the smaller you keep the board the less distance the current has to travel and therefore the less crucial the calculations become.

[Captain Morgan]

Edit oh and tip for jlpcb, if you order the screen it defaults to quite a large dimension, is it 200*200? You can change the paste screen dimension, for the small rc light controller on GitHub I made I just shrunk the screen to be a few cm larger than the pcb in each dimension - it made the postage cheaper too!

All coincidences are only coincidences!



jlpcb - used to have (don't know about it now, I'm ordering PCBs elsewhere now) - had the option to set a custom solder paste stencil size.
I made my "solder paste printer" - for a stencil size of 120 * 120 mm and ordered a stencil exactly 120 * 120 mm in size from jlpcb.

I think I have a list of most common components ready to buy, I will try practical experiments in a breadboard to make sure I understood before I try to draw any circuits, it’s also tempting the more you learn the more you want to try and add to the board!

Now the big problem is to buy radio components that were used in the parent project.
I have produced approximately 13 versions of the TCB PCB, of which there have been approximately five physical versions.

I really want to make a wall-mounted glazed showcase (as a memento of what a fascinating path I have traveled with the creation of LukeZ), which will be in the form of a consistent evolution: Author's board, in the author's design -> my first project (which I will never show to anyone, because there shame and horror) -> other other evolutions.

Even though I made the latest (Version 13, which I showed above, and it works great) in more than three units, I will most likely have to release the 15th version, which will be adapted to use cheaper components than what was - in the parent project. Because they are available for purchase anywhere in the world.

Damn chip crisis! As soon as I began to understand at least a little in this matter - I can’t buy anything now, because manufacturers don’t sell goods to stores.


P.S. I hope I was able to answer all the questions, if something needs clarification - I'm always here, and I'm ready to provide answers, perhaps not always correct and understandable (I spied this answer from one of the participants in this forum, and I liked it).

[whitecitadel]

The XT30s are probably more than adequate for most RC tanks and would take up less space.

I mentioned XT60 as that is the most common connector on my 2S batteries, but your right XT30 for the ESC make a lot more sense.

I agree for such a board copper planes are the way to go instead of traces. Rather than do 50% each, just make the top of the board a single plane and the bottom of the board another plane, that way you can use the entire surface area for both positive and negative. Some fab houses will sell boards with thicker copper (2/3oz instead of 1oz) which can help with current-carrying capacity. Also the smaller you keep the board the less distance the current has to travel and therefore the less crucial the calculations become.

Thanks for tip, I was thinking of upright connectors copying a board I have for Anderson Powerpoles, I had not considered top/bottom planes (not sure how the top would be soldered to the connecter, have to look that up...)

XT30_PCB.jpeg (27.3 KiB) Viewed 3199 times

- Captain Morgan - the first prototype is always the ugly one but that is expected!

[LukeZ]

Thanks for tip, I was thinking of upright connectors copying a board I have for Anderson Powerpoles, I had not considered top/bottom planes (not sure how the top would be soldered to the connecter, have to look that up...)

When you begin designing your board I think this will become clear. But in short, any through-hole has copper both within the hole as well as for a short disc around the hole on both the top and bottom of the board. In the design of the PCB, this hole can be electrically connected to a trace or a plane either on the top or bottom of the board (or both), depending on your preference and requirements. Either way the soldering is still done on the bottom of the board, so no difficulty there for the person doing the assembly.