Totem Mini Lab – testing the Side Panel 1

The Side Panel 1 is powered from the Mini Lab board, using both its 3,3 Volt and the 5 Volt connections.

NOTE: it is very important to set the Side Panel 1 to the same voltage as has been set in the TotemDuino in the Mini Lab! Otherwise things can go ‘poof’…

Let’s take it from the top to the bottom…


The power connections

Side Panel 1 – Power connections

All the way at the top we find three power connections, 3,3 Volt / 5 Volt / GND. They should be connected to the Mini Lab board. All of them! Even when you’re using the Side Panel 1 at its 3,3 Volt setting, you still have to connect the 5 Volts as well, see below with the relay description.


Power selection jumper

Side Panel 1 – JP 7 – power selection jumper

Half way down the board on its right side we have a small section that reads: OBS! Select VCC. It contains one jumper – JP7 – that can take two positions, connecting the middle pin to either the upper (for 3,3 Volt VCC) or the lower one (for 5 Volt VCC).









Three push-push switches with LED indicators

Side Panel 1 – DPDT switches – schematic
Side Panel 1 – DPDT switches

These switches are DPDT switches, meaning that they have two contacts with three connections each. A middle contact that is connected to one – and only one – of the other two connections (One is Normally Open, the other Normally Closed). The two contacts per switch move at the same time. Our friends at Totem made use of this fact to expose one contact to us for experimenting use and the other one to drive a LED, indicating the status of the switch. The LED, when lit, indicates that the switch has been pushed and that the Normally Open contact is now closed. The switches and the LED indicators work fine, on both 3,3 and 5 Volt setting.


Three 10K potentiometers

Side Panel 1 – potentiometers

Next from the top are three potentiometers, basically variable resistors with a range of 10 kilo Ohms. They are labeled A, B and C, from left to right.

Side Panel 1 – potentiometer schematic





Each potentiometer has three connections. The two outer connections can be set to GND and your chosen VCC with two jumpers, mounted above the potentiometer.

This gives you the possibility to generate a different variable voltage between 0 and 3,3 or 5 Volts on the middle pin of each of the three potentiometers.

When you remove these jumpers, you can use your own voltages on the two outer connections. Personally, I would recommend leaving the GND jumper in place to establish common ground unless you know what you’re doing…


One rotary encoder switch

Side Panel 1 – Rotary encoder schematic

Next is the rotary encoder switch. I still have to figure out how this thing works exactly.

For sure it has a push action that operates the push switch (P1 – P2 in the schematic). Rotating the knob clock- or counterclockwise seems to give us the same pulse trains.

Research work to be done here…



Three simple push-buttons

Side Panel 1 – push buttons
Side Panel 1 – push buttons

Next: three simple push-buttons, when pushed, giving us a connection to ground. No pull-ups, nothing fancy here.

So we have to arrange for extra circuitry elsewhere (when needed).

No surprises here, they just work.





Side Panel 1 – RGB LED

There’s one RGB LED here. This is a LED with four wires coming out. One side of the housing is (supposed to be) flat, so we can know which orientation we have to put it into our printed circuit board…

Caveat: Put this thing in in the proper orientation or it WILL die…

Side Panel 1 – RGB LED schematic

On the LED I got with the package it was hard – if not impossible – to see which side that was. So I just decided to put it in. And off course, Murphy struck immediately when I started to apply voltages from the potentiometers. My poor LGB LED died on the spot.

Further testing will take place when I receive the replacement LEDs I ordered.

[edit time=”two days later”]

Received the replacement RGB LED that I ordered. Tested it first, and – after following the traces of the PCB – soldered it in. Personally, I think that the resistors of 220 Ohm (certainly on 5 Volt) are to small, the LEDs are very bright! I hooked them up to the potentiometers (if you follow my lead, make sure to set these at half of their range) and was able to play with the RGB.



One relay

Side Panel 1 – relay schematic
Side Panel 1 – relay

There’s one relay on the bottom right side of the Side Panel 1. Basically, a relay is an electrical switch, often used to switch on and off things outside it’s circuit that need way more power than the circuitry can provide. It has the advantage of being able to totally isolate the switched circuit from our current circuit. The relay that has been mounted on the Side Panel 1 can switch stuff up to 250 Volts and it can carry up to 10 Amperes…

Caveat: Do not go over 30 Volts when you are a beginner, it can kill or at least injure you!

Normally, a relay draws to much current for a little microprocessor like our Arduino. To overcome that, an amplifier is needed. In this case a transistor (Q4 in the schematic) is used to bridge that. Now we can ‘drive’ the transistor with a small current, causing the transistor to ‘drive’ the relay with a bigger current.

Although the printing on the PCB (Printed Circuit Board) says ‘+3-5V=ON’, the relay will not activate when the TotemDuino, the Mini Lab and the Side Panel 1 or set to operate on 3,3 Volt AND the 5 Volt power connection has not been made.

Caveat: DO connect both voltages to the power connectors from the Mini Lab!

Relay on 3,3 Volts:

I connected the contacts of the relay to my continuity meter, so when the relay makes contact we should hear a sound. We don’t… So the relay, as mentioned above, will not work when only the 3,3 Volt power is connected.

Relay on 5 Volts:

I connected the contacts of the relay to my continuity meter, so when the relay makes contact we hear a sound. It works, also when the whole system is set to operate on 3,3 Volts, provided the 5 Volt connection from the Mini Lab IS connected!

One 3,5mm jack connector

Side Panel 1 – Jack plug
Side Panel 1 – Jack plug schematic

Last but not least, there is a 3,5mm jack connector mounted on the Side Panel 1. We can use it to connect the board to or from audio, or to all kinds of other stuff…

Just to be consistent I will put the schematic here, but it’s quite straight forward really… 😉





Summary and conclusion

The different parts work as they should. Some suggestions for possible improvement:

  • More attention is needed in the documentation on how to mount the RGB LED.
  • The rotary encoder could need some explanation; more than just: it’s there and here’s the schematic.
  • I’m sure I’m not alone in my assumption that the relay would work when only the 3,3 Volt power is connected; the fact that also the 5 Volt power is needed, even when the system is set to operate on 3,3 Volts should be mentioned in the manual.
  • Perhaps reconsider the value of the RGB LED resistors?

But, all in all, the Side Panel 1 is a nice addition for the Mini Lab.
















Totem Mini Lab – testing the Side Panel 1