Welcome back to the factory. This week, a lot of LEDs. We've assembled a 3x3 of the GlowBit matrix, the 8x8 matrix in a tiling pattern. We also have another interesting tiling idea on the bake. We'll also cover a new motor driver. Let's do it. And first order of business today is to round out the GlowBit 8x8 matrix story. Here we have an assembled prototype finally of the 8x8 matrix. And it is just wonderful. Taking a look at the back, you can see we had no trouble soldering this bare wire onto those large pads that we were discussing in a previous episode. And I had my concerns about soldering to these pads and whether we would start dropping LEDs off the front, but without any like real care, these just went on super easily and not a problem with any components on the front falling off. So yeah, that's a win.

We busted out the FLIR and ran this at full brightness and it is capable of getting pretty hot on the backside. We measured around 60-degrees Celsius. And so that's probably at the upper limit of what you would want these diode temperatures to be running out. So you can definitely send them pretty hot, but of course you can't be mad to drive these at full brightness anyway, because you can get so much out of them from, you know, like 20, 30, 50%.

What about the tiling? Well, I'm very pleased to say that we also ran a few boards through the pick and place machine and made this tile, this 3x3 tile, and it's got some weight in it. We put this together to test the tiling philosophy, whether the gaps were appropriate, whether the solder pads were about the right size. And I'm pleased to say that it was a resounding success. We were able to power this entire 3x3 tile.By using a 3x3 matrix, we were able to distribute power from the center to all the edge connectors without any wiring. The signal path was routed from the top right, snaking down through each tile in a serpentine pattern. Soldering the D out to D in connections was straightforward. Aligning the rows was also easy, as we simply placed the tiles face down on a silicone mat and soldered the bridges together. Everything lined up nicely, although there is a possibility of introducing a slight rotation with each tiling. However, with careful handling, it is not difficult to align them perfectly. The panels and stencils have been submitted and are on their way to you via our new production line.

We also wanted to give you a sneak peek at another tileable LED design we are working on. Currently, we are experimenting with tileable triangles. The idea is to create abstract 2D artwork using these triangles. In our test, we tiled four of them to form a larger triangle. We are even exploring the possibility of creating 3D geometries with these tiles. However, this poses a more challenging problem because closing a 3D volume with a three-sided object requires careful alignment of the pins to avoid shorting power to ground or D out to another D out. Nevertheless, we are determined to find a solution for this interesting problem.

In the image provided, you can see that the lower left unit is where power and data are connected.So, how do you tile something like this as a linear address so that every LED falls in a single dimension array rather than having the signal come into the central unit and then simply fork to each of the other units, which would basically give you a repeating pattern on those two units? How do you uniquely address all of these? We've included a loop back net in the center of every tile. In each tile, there is a loop pad that is connected to every other loop pad. This means that we can pass the signal into the lower left tile, go into the middle, and then it looks like we are going up to the top tile through the D0 and DI connectors. Then we come back down through the loop connector and loop out to the last tile at the bottom right.

To enable the loop connection, you just need to solder the D1 jumper, which connects the DI pad to the loop pad. So, even though geometrically we have this fan out where you would probably expect to have a repeated signal on these two units, we actually snake up and then back down so we can uniquely address every LED on this tile. It's still early days for tileable triangles, but I think we're really onto something here. I'm really excited to see what crazy shapes you can make out of these simple tiles. Maybe we'll have to introduce a rectangular tile to pad out the system and give you a few more options. In any case, it's going to be good.

Moving on to more maker fundamental maker essential gear, we've covered proto boards and real-time clocks. What's next on the list? I think it's probably motor drivers. Motors make their way into so many projects. So, we've put together this rather...Nice little two amp motor driver board. So this little chip is just a dual H bridge, just like you're familiar with for driving, say two DC motors bi-directionally or for driving a single stepper in any direction.

This is a pretty nice chip. It's the TC78H660. But quite a nice feature is that it has a user programmable current limit. So as we'll ship these, it will have the current limit set to the maximum of about two amps. But with the inclusion of a potentiometer, you can BYO a 10K pot and set some other current limit to protect, say really small motors or to set some kind of torque limit on your stepper motor, even just to protect the rest of your circuit. Having current limit built in is really nice. And so this has the standard control modes that you'd be used to with a dual H bridge, which is like the in one A, in one B, in two A, in two B, just so you've got a four pin control for two independent motors. But as we ship it, it will arrive in the direction and PWM mode, which is a little more beginner friendly. I think it's a little easier to program around because you just set a direction and then some speed.

We've actually made this footprint as compatible with as many potentiometers as we can. You can use these nice finger turn pots that will just fit on the triangular pads, the very cheap pressed metal ones, which need to use that pad that's all the way up there on its own. And that's probably the one you'd use the most for this kind of thing. Something that's very set and forget, but Hey, if you really want to get precise with it, you can also fit one of these 10 turn or even 25 turn pots across that pad, just like so. And so the way current limiting is set up with the potentiometer is that you just measure. The voltage of a test point and the relationship is known. You get 1.1 amps per volt at that test point. So you just probe that point and turn your pot until you get, say, I don't know, 0.5 volts. And then you know that you're going to get 0.55 amps current limiting.

Just to give you a preview of the schematic design. Here it is. We have our motor driver, of course, in the center, a bunch of, you know, supporting capacitors, et cetera. But I think the interesting part is what happens on the Vref pin. This is where you set the current limiting. And if we follow that out, we've got a cap for some filtering. We come to our potentiometer. The potentiometer is fed from the supply voltage and that could be up to 18 volts. So, you know, if you had, if you had a 18 volt supply running your motor, you would have such a small range on that potentiometer that was actually between say zero and two volts, which is the maximum current for this device.

And so we need a voltage reference to set the maximum current allowable. And that's where this Zener diode comes in. Well, it is actually a voltage reference, but from VCC, which could be, you know, three to 18 volts, we go through a current limiting resistor and into our reference. And so now coming out of our reference, this is a stable, I think it's about 2.1 volts. Is that right? 2.5, 2.5 volts fact-checked. So we have 2.5 volts on this net and now when our potentiometer goes in, we'll be able to use the full sweep of its, its angular resolution to go from zero to two amps.

These other resistors are just here to pre-configure for the maximum current. What this also means is you don't necessarily have to put a potentiometer in here. You could put a single resistor between pins.One and two, and then that would form a voltage divider between your fixed resistor and this 14K pot going to ground. A little bit of an advanced feature, but hey, if you know that you want an exact current and you don't want to dicker around with potentiometers, just bang a resistor in there.

We've also got some reverse polarity protection by means of a P-channel MOSFET acting as an ideal diode. This is a pretty common way to do reverse polarity protection. You know, a lot of P-channel MOSFETs will drop a smaller voltage than say a Schottky diode. So you dissipate less heat, of course, because our supply voltage could be quite high on this VDC input. We actually use the power indicator LED as a clamp so that the gate cannot be drawn too far below VCC. And that way we won't exceed the maximum VGS for this part.

So there you have it more tileable blinkies and a very flexible motor driver. Let me know what you'd like to make out of something like this or what we should work on next in our like Maker Essentials series of hardware.

Until next time, thanks for watching.