What do you think of this NPFA20 compliant diesel fire pump panel? - Page 1
Forum section: electronics / projects

author: rvalente
author_rank: Frequent Contributor
timestamp: November 01, 2019, 10:09:29 pm
content: Hello Mates,I do not have the intention to criticize this company work, just want to know your thoughts about this construction pros and cons

author: Gregg
author_rank: Super Contributor
timestamp: November 01, 2019, 10:49:19 pm
content: It is very neat and tidy. Maybe you can post a copy of a block diagram or schematic so we can see why it needs to be so complicated.I have only worked on old school relay logic fire pump controls which were very robust and quite easy to troubleshoot.Then there is trusting lives to an Arduino questions.

author: rvalente
author_rank: Frequent Contributor
timestamp: November 01, 2019, 11:07:19 pm
content: Attached is the schematics, its in portuguese but, google can helphttps://drive.google.com/drive/folders/1OXi2Jw7xf9LyVUrQ9oulzOOlMF8eJ4fP?usp=sharing

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 01, 2019, 11:30:03 pm
content: Quote from: Gregg on November 01, 2019, 10:49:19 pmI'm going to guess the Arduino is only for functions that are not safety critical like data logging while the PLC does the safety critical stuff.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: November 01, 2019, 11:51:25 pm
content: Well, it might be perfectly legal, but I do not like the practice of mounting naked PCBs in switchgear cabinets like this one.A certain form of build will cause the people to treat it in the same way. Like opening the cabinet and turning around with a extension cord swinging -BOP!- onto the PCB.

author: Gregg
author_rank: Super Contributor
timestamp: November 02, 2019, 12:09:16 am
content: I wouldn’t call it a switchgear cabinet; it is a control cabinet for a diesel powered fire pump. In some jurisdictions, only licensed personnel are allowed to mess around inside fire panels. It is painted red to tell the world that it is fire protection equipment.I only gave the manuals a cursory glance, but it appears to do much more than just control the fire pump.

author: janoc
author_rank: Super Contributor
timestamp: November 02, 2019, 12:21:17 am
content: If this is for fire stuff, then I would assume that someone had to certify it, no? In that case it really doesn't matter whether they use a PLC there or an Arduino Mega and a custom relay board.The Mega is obviously reading some sensors too, doing stuff like that (especially if math is required) on a PLC can be a royal pain in the butt if the sensors aren't the common industrial stuff (like thermocouples, current loops or something resembling a switch).Another thing is cost - a PLC with this much I/O is going to cost around 1000 euro, depending on manufacturer, model and especially if you need fancier I/O then just digital on/off (whether relay or transistors switched). Then you may need development tools (depends on vendor - some like ABB have free tools, others don't).Compared to that Arduino Mega is some 20 bucks (they even used a genuine one), the relay board is likely custom, but certainly less than about 100-200 euro. If it does the job and satisfies the requirements, solution like this could make a lot of sense. I wonder why they didn't integrate the ATMega MCU directly on the main board instead of using the Arduino module, but I guess they had some reasons ...

author: Rerouter
author_rank: Super Contributor
timestamp: November 02, 2019, 12:55:30 am
content: The choice of the module, probably involved a few things,1. Allow easy swap out to rule out what half the the controller has an issue (If a PLC has a faulty IO, you generally need to blindly replace the whole thing)2. Minimal cost solution, The I/O board can be a cheap 2 layer board, with simple routing, while the mega is pretty complicated for the form factor it is in.3. Developer was most familiar with it4. The arduino boards can be cheaper than you can match on BOM cost alone5. Easy for a customer to replace / load upgrades to without specialized tooling.

author: floobydust
author_rank: Super Contributor
timestamp: November 02, 2019, 01:45:45 am
content: The wiring is neat and pretty, NFPA20 has a lot of earthquake and fire clauses for control panels.Things that might be improved;I see AC mains circuit breakers but no fuses/disconnects for the batteries and DC gear. Where are the fuses for the battery power?You don't put knockouts and cable glands on the cabinet top. Water gets in and the PLC might get wet. The bottom knockout is missing a nut. Who ever installed this lovely panel is an idiot.I would not have Arduino I/O running on a long ribbon cable, or put an LM2596 switcher next to hall-effect current-sensors. The electrolytic capacitors look cheap, where are the UCC or Nichicons.

author: rvalente
author_rank: Frequent Contributor
timestamp: November 02, 2019, 11:01:17 am
content: Quote from: NiHaoMike on November 01, 2019, 11:30:03 pmI believe so, the manual wont tell me how this uC relay board works, I believe since there is an SD card is for logging purposes, but you can not see the logs in the displayQuote from: Neomys Sapiens on November 01, 2019, 11:51:25 pmI believe they should have put the boards in a metal enclosure, laser cutting is so cheap these daysQuote from: janoc on November 02, 2019, 12:21:17 amThe small plc handles the engine start, its a 12V small plc (similar to logo), the big board is in parallel, maybe some redundancy I believe. The PLC cost for this project would be much more expensive and there is not many options in 12V.I'm not sure if NFPA20 requires certification like the FM Global does, this controller is not certified, only compliant I believe soQuote from: floobydust on November 02, 2019, 01:45:45 amThere is four circuit breakers, one for each baterry charger (only switch one mains live) and one for each battery, no fuses.

author: dom0
author_rank: Super Contributor
timestamp: November 02, 2019, 01:53:25 pm
content: Routing 30 V working voltage ribbon cable in the same conduit as mains cables usually doesn't fly, because the basic rule is that the insulation of every cable in a conduit has to handle the highest nominal voltage in the conduit. That's why all bog-standard industrial control cables are rated for 300 V.

author: coppercone2
author_rank: Super Contributor
timestamp: November 03, 2019, 10:06:54 pm
content: Quote from: Neomys Sapiens on November 01, 2019, 11:51:25 pmthat was a fight with management or an ass kisser behind thatalso, no strain relief behind solder junctions to screw terminals. Its hooked on the cable management comb. Probably should have zip ties.those screw terminals in the circuit breakers are press formed from solid metal, not bonded with solder. Its a different system that looks the same.And I don't know about using an arduino as a riser board for a fire safety system is a good idea. It should be one board. Why is it done this way?

author: rvalente
author_rank: Frequent Contributor
timestamp: November 04, 2019, 01:45:48 pm
content: I do not like either the naked pcb, they could've add a small steel enclosure from laser cutting, cheapThe strain relief would be a good point, but I've seen various industrial controls (check S7 1200) has no strain relief eitherI believe they've used the arduino to avoid sourcing more components, they could have just pasted the atmega ic on the board

author: German_EE
author_rank: Super Contributor
timestamp: November 04, 2019, 05:44:05 pm
content: I would have mounted the PCBs in plastic boxes with labels on the top saying what they do. I also don't like the idea of ribbon cables in the same trunking as mains cables.

author: coppercone2
author_rank: Super Contributor
timestamp: November 04, 2019, 11:12:21 pm
content: I thought this is a supply chain problem to use arduino because you cannot get them to manufacture more real arduinos on demand, only what is on market?

author: DBecker
author_rank: Frequent Contributor
timestamp: November 05, 2019, 06:37:28 pm
content: Quote from: coppercone2 on November 04, 2019, 11:12:21 pmThere are plenty of parts that could be discontinued unexpectedly. The military and automotive industry have expensive processes in place to mitigate that risk. Industrial and consumer products generally don't. Arguably using a mass-produced subassembly is likely to provide better availability of NOS parts than trying to source the original components a few years later.(I still look at any product using an 555 timer or Arduino board as likely having beginner-hobbyist-level hacked together bits elsewhere.)

author: wraper
author_rank: Unknown
timestamp: November 05, 2019, 06:55:03 pm
content: I wonder why in the hell would they put arduino instead of just mounting bare MCU on their custom board. It's not like they can't load the same firmware into it.

author: floobydust
author_rank: Super Contributor
timestamp: November 05, 2019, 07:23:25 pm
content: I can't see where the batteries are actually connected.The fuses should be first at the battery wiring, here they first go to a few terminal blocks, diodes, and relays?Caixa de Transferencia has no fuses. There's three 10A DC fuses/disconnects but they seem to be for the internals PLC, Arduino in the main cabinet.The battery chargers have SKR26/12 blocking diodes at the outputs, so the charging voltage is always low unless the trimpot is cranked up. Equalization mode is not used. The diodes should have a heatsink like they do in the Caixa de Transferencia.I would want the pump to start in an emergency.

author: coppercone2
author_rank: Super Contributor
timestamp: November 05, 2019, 10:57:58 pm
content: Quote from: wraper on November 05, 2019, 06:55:03 pmconvenience if the capabilities are regarded as an offshoot from usual money makers, if you can get away quick with libraries to test market and get sales interested etc.. fast moneyhowever, just the fact that its a fire safety system bothers me a bit

author: wraper
author_rank: Unknown
timestamp: November 05, 2019, 11:25:07 pm
content: Quote from: coppercone2 on November 05, 2019, 10:57:58 pmThere is zero actual convenience. Routing MCU + few passives is not harder than placing all those pin header connectors for Arduino. Also they need to manually solder header connectors to Arduino PCB. Probably after desoldering original ones as I cannot find original Arduino being sold without connectors.

author: floobydust
author_rank: Super Contributor
timestamp: November 06, 2019, 04:05:56 am
content: Um, they desoldered the Arduino Mega connectors and flipped them to the other side? OUCH the burn

author: mjkuwp
author_rank: Unknown
timestamp: November 06, 2019, 04:58:09 pm
content: I don't mind the use of the MEGA but I think they should have flipped the header pattern so that a relatively standard one could be used. I use Arduino boards and Raspberry pi, etc. quite a bit for work and over the years I don't think any of the ATMEL chips have failed. The Raspberry pi boards get upgraded periodically so I have no opportunity to prove longevity but that is off-topic.Here is another option for that boardhttps://www.rugged-circuits.com/mega-techIt is ruggedized - although I do see that the MEGA in this control cabinet is surrounded by protection.I wonder if the engineers chose to use the stock mega board because they lack the tools or knoweldge to burn the bootloaders into the chip. It is a pretty big head-start to have a USB -based serial port and bootloader onboard.

author: wraper
author_rank: Unknown
timestamp: November 06, 2019, 06:41:46 pm
content: Quote from: mjkuwp on November 06, 2019, 04:58:09 pmProbably stupid enough to realize that $2 programmer from China would do the job. It's like c'mon, If you can design that custom board, you should be able to put MCU on board and program it.

author: jbb
author_rank: Super Contributor
timestamp: November 06, 2019, 06:55:24 pm
content: It's generally tidy, but there are some things I would change:Solder the Arduino MCU straight to the IO boardSeparate the wire runs for the AC mains and all the low voltage stuffProvide better cable management of the ribbon cables over to the right (I assume they go to the front panel) to reduce the risk of pinchingTry to get all the external wire entries onto thebottomface of the panel using proper strain relief (improves water resistance and lets you put other panels tightly side by side

author: coppercone2
author_rank: Super Contributor
timestamp: November 06, 2019, 10:29:27 pm
content: Quote from: wraper on November 06, 2019, 06:41:46 pmyea but you can't use a 2 dollar chinese usb thing to program stuff for an assembly line with confidence, maybe they thought arduino company has proper equipment? You would need to tap the signal from the programmer to verify its not damaging the chip etc

author: wraper
author_rank: Unknown
timestamp: November 06, 2019, 10:44:48 pm
content: Quote from: coppercone2 on November 06, 2019, 10:29:27 pmSpend $50 instead and buy PICkit 4.