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I/O, I/O - It’s Off to the Escape Room We Go!

BAC V Front ViewIntroducing our new BAC V with expanded memory, upgraded outputs and more flexibility with the inputs. 

Why is it Called the BAC V?

Internally, it happens to be the 5th revision of the electrical hardware inside of our  "Bad ASS" Controller and while we’ve always made small changes to the hardware to improve it over time. Whenever customers are having an issue, we do our best to fix it. To be pedantic, 5 is the letter "V" in Roman Numerals. We could have called it BAC 2, but we have some other thoughts on that one for the future. Also, "Bad ASS" Controller is long, and since the beginning, we’ve consistently shortened it to BAC internally. We hate name shorteners. Oh well.

So What Did We Change?

There are three 3 major changes. The inputs, the outputs, and the internal storage. There is actually a 4th improvement, but it technically showed up on Rev 4, which was the large expansion header on the side, allowing the FX45 to connect to the BAC.

The Sizzle

I will drone on below about the technical improvements, but you want to know WIIFM (what’s in it for me)?

  • 4 inputs now have the option to be optically isolated (opto) which means more freedom in the way you connect other prop controllers to the BAC. The remaining 4 inputs require a voltage be applied to the input to turn them 'on'. The 'opto' inputs can additionally be turned 'on' by grounding an input or applying a separate power source to the input. Details below.
  • The outputs have a completely new driver. They have built in short circuit protection, will auto reset during brief faults, and can supply a power connection or a ground connection when the output is activated. We're sorry if you had to send a previous BAC back to us for repair of a damaged output driver. This is much better.
  • The internal memory is more robust, larger, and faster. It won’t forget your game.
  • The FX45 expansion board is designed to simplify connections of expansion devices and sensors to the BAC.
  • The BAC V correlates with the new BAC v1.9 firmware and a new BAM. Tons of new features in games and we added remote logging!

The Steak

If you made it to here, give yourself a gold star for hanging in there!


Inputs 0-3 now have the option of being optically isolated. Optical isolation means there is not any electrical connection between the external input circuitry and the internals of the BAC. This can be important for a few reasons:

1. If you have an electrically noisy signal, this noise is less likely to make it into the BAC and cause issues. This can happen with Back-EMF (issues with maglocks and motors) or even 110V lines run around your BAC.
2. Because there is not a direct electrical connection to the BAC, you are free to ‘turn on’ the input however you want. This is what the circuitry looks like:
IO, IO - It’s Off to the Escape Room We Go!-BAC V Jumper Configuration

I know there is a lot going on there. There are two jumpers which configure the way inputs 0-3 work. Next is default configuration, which operates just like the other inputs; by applying voltage to the input pin.

IO, IO - It’s Off to the Escape Room We Go!-Active High Jumpers
IO, IO - It’s Off to the Escape Room We Go!-1-Active High-1

Here, inputs 0-3 'turn on' the input by applying voltage to the input pin. The voltage applied to the input pin is referenced to the BAC Ground. In this configuration, the connections are NOT isolated because the input voltage references (is connected to or is relative to) the BAC Ground.

IO, IO - It’s Off to the Escape Room We Go!-Active Low Jumpers
IO, IO - It’s Off to the Escape Room We Go!-1-Active Low-1


Here, inputs 0-3 "turn on" the input by connecting the input pin to BAC Ground. The voltage applied to the input pin is referenced to the positive voltage of the BAC. In this configuration, the connections are NOT isolated because the input voltage references (is connected to or is relative to) the BAC VIN.

IO, IO - It’s Off to the Escape Room We Go!-Opto Input, External Reference (DOT Negative)Now the fun starts. To maintain reverse compatibility and provide flexibility, the BAC V’s input terminal block has a DOT connection. This connection is located in the red circle with red arrows pointing out the DOT and the terminal. You can also see an illustration for the jumpers to see how they are connected. If you look closely with the input header off, you can see the JP1 jumper below. Side note, we gave you a little spot on the side (white boxes) to mark your settings if you change the jumpers for quick reference (blue box).

BAC V DOT Connection
I digress. In the above illustration (not the picture immediately above), notice how the top jumper, JP2 is off the side and the bottom jumper, JP1, connects the DOT terminal to the Opto COM signal. Now the inputs are optically isolated. And now that they are, you can trigger them (turn on) any new ways!
BAC V HW Update - Opto Input, External Reference (DOT Negative)IO, IO - It’s Off to the Escape Room We Go!-Opto Input External Ref DOT 12-24V

Notice the only difference between the two wiring diagrams is the polarity (direction) of the battery. If you look at the symbol of the Optical Isolator in the image above, specifically the LEDs (the triangles with lines and arrows), they are polarized devices. The fact that the device we used has two LEDs in the package, and they are wired in opposite directions, means that one of them will be on no matter which way you hook up the power. What you do want to keep in mind is that if you have multiple devices you are connecting to the optical inputs, you need to choose a common wire, which is the DOT.

Very important note: With the JP1 jumper in the 1-2 position, the #1 terminal is NO LONGER the positive voltage of the BAC V supply. You can no longer provide power or draw power from this terminal.

Also very important: Do not place the jumpers in any other configuration than those shown. While there may be other useful combinations, JP1 in the 2-3 position while JP2 in the 1-2 position will short the main board supply. Don’t do that. That would be bad.


The output driver has been significantly upgraded. Here is what we had originally.

Output Driver before BAC V

While the driver we used is very popular, it was not flexible and it could break when abused.

The new output driver uses a more sophisticated switch, designed for the automotive industry. It can detect a short circuit and bad connections. It will turn itself off automatically if it detects an error and...wait for it...it will try it 3 times over a few seconds. But wait, there's more! The error light will even flash when this happens. And if that wasn’t enough, there is a new logging system in BAM which will save this information for you so you know when it happens.

These two following 2 schematics show just one of the 6 output channels on each BAC V.

BAC V - Output Driver Upgrade - Low Side SwitchBAC V - Output Driver Upgrade - Hi Side Switch

I get this may be a little confusing, but each output pin has two switches and a controller for each pin. This means that each terminal can close the LS switch and connect the pin to ground OR close the HS switch and connect the pin to VIN (usually 12 or 24V).

You can configure this option in BAM on the Hardware -> Configure IO page.

IO, IO - It’s Off to the Escape Room We Go!-Output Driver Modes

Referencing the images above, here are how the options work.

Low Side - Only the LS switches are enabled when you turn on the output.  Use this setting to 'complete the circuit to turn on a device with a ground connection.

High Side - Only the HS switches are enabled when you turn on the output.  Use this setting to 'complete the circuit to turn on a device with a power connection.

Half Bridge Low - Just like Low Side, but when the output is off, the HS switch turns on automatically. 

Half Bridge High - Just like High Side, but when the output is off, the LS switch turn on automatically.

*The bridge modes are most useful for maglocks and motors.  

The BAC V ships with the default of Low Side to maintain compatibility with the BAC. We chose to use a light to demonstrate the High Side switch as it may be more intuitive to think about switching the power to the light (instead of connecting a ground to complete the circuit). Maglocks should be wired such that the ground is switched (Low Side). There are a lot of real and fuzzy reasons for this. Just do it. But that’s not all this output driver can do.

Speaking of maglocks, the reason they are such a pain to work with is they make this nasty electrical noise when they turn off. We could easily count 100 posts in the Facebook groups about how everything works until you turn off a maglock in a room. So this driver has one more feature that comes in very handy for maglocks, or any other electromagnetic device for that matter. While the controller will turn on the Low Side switch to power the maglock, to disengage the maglock, it will then turn off the Low Side switch and turn on the High Side switch! This effectively shorts the maglock to itself and makes the magnetic field collapse quickly making the maglock release quickly. As an added bonus, it also helps minimize the electrical noise they throw off.

Important: Use the Half Bridge Low setting for this feature when using maglocks.

Outputs are still rated at 500mA, but with the built-in protection, it's way more forgiving if you push the limit.

The other modes may be used if you know what you are doing. 😊 They effectively act opposite. For instance you can select Low Side and control a light in the same wiring as the maglock.

Internal Storage

Admittedly, this is a long and boring story. So in short, way back when, before there was a BAC, there was an FX450. The main processor did not have the configuration storage capabilities of the FX350’s processor so we added on some I2C EEPROM. The FX450 evolved into the BAC and all was well with the world, for a while.

Then the BAC got a lot more complicated. It grew and expanded. Audio boards, FX20 Displays, FX51SEN, etc. Unfortunately, this meant that the same interface being used for the critical configuration was also being used for peripherals and sensors. So there were some unforeseen issues.

So we rewired it! The new memory device is much larger and uses the SPI bus, which is NOT exposed to the outside world and is much faster. But don't worry, I’m sure we’ll figure out something to do with all that storage!

Expansion Header

A 26 pin header is exposed on the right hand side of the enclosure. As the product evolved, we felt customers should NOT have to open the case for connecting expansion peripherals. (We solved the update process along time.) The FX45 comes in two varieties, a basic and advanced. The basic provides the expansion headers for RFID and sensors like the FX201 and FX51SEN. The advanced version provides 2x Neopixel interfaces and holding hands game interface and a few other features.

We’ve been busy. Covid sucks, but we are still here making things better for the Escape Room industry. Check out our latest controller, the BAC V and reach out to us if there is anything we can do to help you take control of your escape room!

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