TZT2 voltage sensitivity

[stevemitchell]

I have two brand new TZT2 12" displays I added to my flybridge about 2 months ago. They are powered by a dedicated circuit that has both the TZTs, DRS4D-NXT, and Furuno switch. I have both TZTs wired per the manual, with ferrite as close as possible to the power connector, and separate ground wire. This circuit has been in place for many years, and powered older vx2 series Furuno equipment which was super power hungry compared to the TZT+DRS.

I have a considerable NMEA 2000 network along with a lot of other things which you can see here https://sailbits.com/content/images/2019/03/Rendezvous-Network-2.png

My house bank powers all of these devices at 12V and is also responsible for my windlass. This setup has been working on this boat fine for 30 years prior to me purchasing it. It would be more ideal to have a separate battery or battery bank for the windlass, but I see no reason to change it at this time.

While using the windlass, voltages can drop, especially if I have been at anchor, and the TZT2's reboot almost every time. Not a single other device on the network, including other Furuno products, Raymarine Axiom, B&G, NMEA 2000 powered devices, reboots - only the TZT2s.

After a lot of troubleshooting, it appears this is related to the voltage drop, and it is surprising to me that the TZTs are so vulnerable to this while everything else is not. I have since added a DC-to-DC isolated power converter from Victron to ensure that the circuit at the flybridge always gets 12V and that has solved the problem for now.

Is this a known issue with the TZT2s?

 

[Johnny Electron]

No what you describe is a common problem with boats. Back in the day we had customers with Vx2s and sounder rebooting due to bad power. Power distribution can allow voltage to be at different levels depending on the cable runs and where it falls in the distribution. 30 year old wiring is also subject to corrosion and extra power loss/drop. It is really common on boats for people to get shutdowns of assorted electronics when starting engines. When the engines take all the amps for the starters the electronics can experience a power drop if the batteries and wiring don't offer enough capacity. This is exactly why NewMar makes a device like the "Start Guard" to clean and boost the power during drops. Bad power is bad power and not something you want to run your electronics off of.

 

[stevemitchell]

I don't believe I have "bad power" here as it is powering a ton of other electronics without any issues. I've also moved the TZT2's to another circuit and the same thing happens. Voltage drops are a fact of life on boats, and while we all try to eliminate them, there will always be fluctuations.

Also, there is no starting circuit involved in this, that is a completely separate battery bank. The wire is in good condition, oversized for the amp draw, and I've tested a number of other things. Part of my day job is working on boat electrical systems, so I am not a random DIY'er that doesn't understand the more intricate workings of a boat electrical system.

It clearly seems like the TZT2 line is ultra-sensitive to voltage drops, whereas the RD-33s, FM-4800, NavPilot 300, Raymarine Axioms, B&G Vulcan, and at least 5 other large MFD style devices aren't.

I'm happy to have found a workaround, but at an additional cost. I guess I was hoping to find out if there is a lower tolerance with the TZT2 series than previous products.

 

[Taniwani]

I think starting your windlass simply drops the voltage level low enough for long enough for the TZT2 to cut out. I had the TZT2 on a lab power supply while I was playing with it at home and found that it shuts out 10.1V, but I haven't checked how long it holds out at a lower level.

I'm running mine on a 24V system and my worry was the bow thruster of 8kW where I measured the voltage on the batteries to drop to 15.5V for 210ms before coming back up to 22V while running and nicely recovering to 25V when it stops. The TZT2's are completely unimpressed by that. The surge as such is clearly no problem, they may just starve in your case with their converter PWM maxed out.

 

[Pthein]

Out of curiosity what’s the battery condition? I have seen these problems manifest themselves and the culprit being the battery starting to age. Have you load tested the batteries and confirmed electrolyte levels etc.

 

[stevemitchell]

My point has been that all of the other vendor equipment does not do this. The TZT2s seem ultra sensitive to this condition.

Batteries are nearly new, nothing else has an issue, only the TZT2s.

 

[Taniwani]

Steve,

I understand what you are saying and can see why you would be disappointed with the behaviour of the TFT2s. But let me offer a different perspective on that topic, as I think the issue you are seeing might be the result of good design practise.

You pointed out, that your TZT2s are rebooting by themselves and if I understand that correctly, not powering down to power off state, requiring you to press power on to bring them back up. What that means is, they are aware of a short power drop, as opposed to a longer shut down.

A good design praxis is, to signal the MCU that a power loss is imminent, so that you can get to a controlled rest and not run in danger corrupting data during a critical operation like a flash memory write. You usually design the power supply to give you some guaranteed run time, after signalling power loss, enough to do a controlled shut down.

So in order to make that work, you will need to define a minimum voltage level and a time that you maximally allow the voltage to be below such level, before raising the alarm.

And once you have initiated the shutdown, you are committed even if the power comes back in the mean time.

Not doing all this and just riding out the short drop with energy buffered in the power supply, you run the risk to garble up some data if it lasts longer than that. You could certainly argue that there isn't really much to garble up in these instruments, but an MFD could certainly store corrupted track points of mess up the odometer.

Just the view of an engineer to consider.

 

[stevemitchell]

Thank you for the engineering perspective. I think that is a good way to design a product, and I have seen it happen before on many other things both in the marine world, and the technology world where I am part of hardware design and testing