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Forum Index : Microcontroller and PC projects : 12v DC UPS?
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| Tinine Guru  Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
My controller supply needs to be in the range of 11 to 13v. I would like to keep the controller alive in the event of the main power switch being turned off. I am interested in both short-term (minutes) and longer-term solutions. Endless options out there but I prefer to seek recommendations from those who maybe have some experience with this stuff.  Craig |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5091 |
If you need power over a certain period, it is always usefull to know how much... min and max please. Easiest is a lead acid battery on trickle charge (decent energy, and good lifetime, simple charger). That is why they are used is virtually all emergency exit lights. Volhout PicomiteVGA PETSCII ROBOTS |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Sorry bud, meant to state that I guesstimate ~36W. Lead acid is a bit 20th century but I just found this thing interesting: I confess that the "whiz-bang" features interest me because I have an Android tablet for the HMI and clients tend to love this stuff.  What do you think? Craig |
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CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2170 |
+1 on the LA thing. just the easiest trickler to build and plenty of grunt. Edited 2022-11-02 01:02 by CaptainBoing |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
KISS is the thing for a UPS. Complicated enough but no more. It *has* to work first time every time and fixable in 5s if it doesn't. Lead-acid technology has the advantages for a UPS in that it is cheap and will take a lot of hammer. You can run right down to almost flat repeatedly. Use one to feed a DC/DC converter for your load to keep the output voltage constant. It's not pretty or ultra modern but it works and there's little chance of it bursting into flames. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
I should explain. This is one of those nice-to-have features that no-one in my industry offers. The machine is supplied with 3-phase`and I have a 12v PSU to supply the controller. The UPS can be bypassed should it fail. The reason for this battery backup is that; occasionally, a servo-motor-amplifier might fault-out and the only way to clear the fault on many machines is to cycle the main power. When power to the control is lost, all the axes (incremental encoders) lose their position and so, on power-up, all the axes need to be re-homed. This is a big enough pain in the buttski on a 3-axis machine let alone 6/9/12 axes, especially because this usually happens during the process of forming very expensive material. Not only does someone need to bypass the safeties to go and retrieve the scrapped material but in the case of a work-cell, the robots all need to start-over (not fun). I can't believe that others haven't come-up with this simple solution. In fact, on other equipment, it only needs an operator to panic and hit the e-stop and everything has to start over. Not the case with my systems, one can simply start-up and resume. Craig |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Oh, it's pretty ok. Personally I think it's severe overkill. All you need from a UPS is a warning that the battery is getting low and you'd better get ready for a dead system. Anything else is useful to a battery diagnostician but shouldn't be viewable by the end user. They get easily confused and will ask you all sorts of irrelevant questions. :) A UPS for the control system is a good idea. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5091 |
Hi Tinine, Is there an option in going down controlled (in stead of staying awake?) Just a small battery for the controller heart, writing current state to non-volatile memory (SD card, or MMBasic VAR SAVE). And then going down with the rest. Or do you have to keep more electronics (that are beyond your control) alive to prevent homing again ? Volhout Anyway, I still vote for a lead acid battery. The 3A (36W) is easy for a 12V 10Ah block. And you adjust your 12V power supply to 14V, connect it to the lead acid battery through a 10A shottky diode. And run the whole controller off the battery. UPS guaranteed... PicomiteVGA PETSCII ROBOTS |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
The encoders and the encoder counters (P2 in my case) must remain powered-up because some external force could physically move the axes during power-down. We are only talking about a short period of time, enough to reset the servo-amplifier that faulted (no external reset on many models). I have found a vendor of super capacitor devices that might be the perfect solution Craig |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3378 |
For a short time period, why not a simple 12V power pack? In the next month or so I will also be checking out these 12V 18650 battery packs. (I'm certain they're lying through their teeth about 50Ahr, but I'll test to see what they're capable of.) PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Hey, nice one I don't believe the spec but it's a cool device, regardless. Think I'll order one tomorrow. Cheers, bud Craig |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Didn't go for it because none of my 18650 battery-packs will output while charging. I guess the BMS kills the output when charging  Craig |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3378 |
The single-cell 5V & 3V3 18650 modules that I have used will output while charging unless they have shut off when disconnected from power because of low-battery. Then I've found they will neither charge nor power the device, and you have to turn off the 5V USB switch to get them to re-charge. That pretty much defeats the purpose, but I fixed that by running a wire plus schottky diode directly from the 5V input power to the 5V USB pin (plus another schottky diode from the switch to 5V USB). Then it cleanly starts up when power is re-applied, and the battery slowly charges. I'll still try that 6-cell 12V 18650 pack. Maybe instead of 50,000mAhrs they mean 50,000mWhrs @ 12V, so about 4Ahrs. That might barely be plausible, though I suspect it's still high. I may also look at this claimed 10Ahr 12V UPS PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Too funny....that one is already in my shopping cart. There is also a version without the extra ports. I have messaged them for full documentation. Clearly it's AC input but many of the vendors state 12.7V DC input. The sum of all outputs mustn't exceed 2A which strikes me as a bit puny. Craig |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Duplication Edited 2022-11-03 07:31 by Tinine |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
The 2A limit might be because the output is from a DC/DC converter with only one, or possibly two in series, 18650 powering it. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3378 |
If it's anywhere close to 10Ahr @ 12V it has to have more than 2 18650 batteries. I looked for a youtube teardown but couldn't find one. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
@lizby Kinda liking this schottky diode idea, actually Craig |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
PITA duplicate again. Edited 2022-11-03 10:54 by Tinine |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
You can easily get variable voltage from about 1v up to 50V out of a single 18650. Just use a buck-boost converter. You get shorter running times at higher output voltages at it depends on the Watts load. 2A at 12V is a 24W load. At 7.2V you'll draw about 3.7A from the batteries. At (a very optimistic "Chinese") 3Ah capacity you should get about 50mins run time. If you put 3 "Chinese 3300mAh" 18650s in parallel you get 10Ah (well, 9.9Ah, which is close enough for advertisers). You *might* just see it with new batteries but not for long. At 2V 2A out of the buck-boost converter you could be discharging the parallel set at 7.5A or so. Xtar claim a maximum current of 10A for their version so this looks possible, Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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