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Forum Index : Microcontroller and PC projects : SMALL UPS...
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
Hi all.  I'm looking for a SMALL UPS. It must output 230v, but be as small as possible. The connected load is only 15-20W. I want to add UPS's to the TV distribution amplifiers at the local village, cos if a house is vacated or is being renovated, the main power is switched off - which kills the distribution amplifier, and dozens of houses loose their TV service. Ironically, following the 2016 lightning strike that destroyed the old system, the new system uses Televes launch amps out in the field, and they are excellent, with slope adjust and equalizing etc - way better at maintaining a stable TV system then the old amps that got blown to bits, but the old Kingray amps did have the advantage that they used DC power supplies, whereas the Televes ones are mains powered, so I need a mains-power backup solution - but it has to be as small as possible. Anyone got any ideas or links? As I say, the load is tiny - 20W or so, so something as small as possible, should be viable, where it would not be if the UPS had to have more grunt.  Smoke makes things work. When the smoke gets out, it stops! |
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 6781 |
Is there no way to bypass the power supply and feed them with DC directly? It would be a lot easier. Trouble is, at this point in the chain you probably don't want to be introducing mains supply noise, which makes any UPS a bit more complicated. The cheap end aren't true sine wave inverters. The size is very much going to depend on the battery, which depends on how long you want it to run for. If you can't find a commercial one, I'd suggest using a RP2040-Zero to generate a nice fixed sine wave. Then (maybe use a pot to set the voltage) level) into any cheap-n-cheerful Chinese 50W or so mono amp driving a little mains transformer in reverse from a 6V motorbike battery - you probably want this to be rugged. The RP2040-Zero could handle mains detection and give a bit of overrun when it returns and could also start/stop the sine wave as necessary. It could also monitor the battery voltage and switch the charger into boost mode when needed. Keep the battery on continuous trickle charge while it powers the inverter. No changeover to bother about then. LM317T would be a suitable device for the charger when fed from a simple power supply, I think. Edited 2024-05-29 17:31 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
That is the way I would do it. Assuming this is a "Daisy Chain" system with a booster-splitter at each unit. Power in any unit goes off and the rest of the chain is off. In the ones I have worked on the 240V supply produces 12 to 15VDC for the amp. A small 12V SLA battery and 12V plug-pack SLA float charger at each unit would work. The other option is to couple 24VAC** into the coax with an RF choke at the head end. In each booster-splitter tap off the 24V with a RF choke. Halfwave rectify, filter and regulate that down to the required voltage. The RF choke also passes the 24VAC from the input to the downstream output. The amp circuits usually have small capacitors on the input and output. If not add 100pF to the input and output to keep the 50Hz out of the amp. At the head end the masthead amp and 24V transformer could be fed from a regular UPS. ** AC is normally used to prevent corrosion of the coax in humid weather. Edited 2024-05-30 07:33 by phil99 |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
I will look into the possibility of hacking the amps then. Any mains-power UPS has to be small, as these amps are inside waterproof outdoor boxes with doors, recessed into the house brickwork. That gives me nice easy access to the services without needing to get inside the house, but space is limited. Even a STANDARD little 5-10 minute backup UPS would be too big to fit I think. I therefore, might be chasing something that is simply impossible to do, and the low-voltage concept - perhaps adding a simple diode-gate to prevent the external battery from trying to back-feed into the output of the on-board PSU if the mains fails - might be a good idea after all. I just did not really want to hack the amps, but sometimes..... EDIT: And a small SLA battery, would be able to run the amp for hours on end no problems due to the tiny load the amp represents, so there is that.  Edited 2024-05-30 09:25 by Grogster Smoke makes things work. When the smoke gets out, it stops! |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
The first step is to measure the DC volts. I think some newer boosters may use a 5V IC instead of transistors, so a 6V SLA may be better for them. It might be possible to use each amps internal supply to maintain the SLA battery. If the voltage is high enough use a regulator set to 13.5V (or 6.7V) to charge it. If not use a diode / capacitor voltage doubler to feed the regulator. There are also tiny DC/DC boost regulator modules on AE. The amp DC current in the ones I have worked on has been from 30mA to 80mA. Edited 2024-05-30 10:15 by phil99 |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
Agreed. The first step, will be to see if I can get a replacement amp, that I can pull to bits to examine the PSU side of things. Unfortunately, the Televes amps are VERY expensive(~$600 each!), so I will have to convince management we need one to tinker with. They are very, very nice launch amps, but they are horribly expensive. But I guess you get what you pay for, and these ones have never needed touching since they were put in place back in 2016 post lightning strike, and they run 24/7/365, so I guess you are paying for that quality and reliability. I can't really take one out of service to examine it's guts, or I will take out a whole sector of houses TV service - that won't go down well with the residents!  Smoke makes things work. When the smoke gets out, it stops! |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Is it this one? If so that is a much more complex beast than I have worked on. The datasheet says 6.6W 110V to 230V 50/60Hz so probably a switch-mode supply. Not as simple as I had imagined. Data-sheet Edited 2024-05-30 10:46 by phil99 |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2350 |
hi Grogster, is it possible to get low-voltage wiring from a central location to each amplifier? if so, then you could distribute 48v AC to each unit, then at each unit use a voltage doubler to convert this to 90v DCv - if the units use a 110-230v switchmode power supply internally then they should be able to run on this 90v DC, but you would need to check just to be sure. cheers, rob :-) |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
Close, but no cigar!  It is these ones here Smoke makes things work. When the smoke gets out, it stops! |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
Now THAT's an interesting idea, only cos in EVERY SINGLE ACCESS BOX, we have the old grease-filled copper telephone cables looping in and out, and MOST of that is now redundant, as people are being forced off of the copper network, and onto Fiber or Wireless for their phone and internet. So, the village basically has a MOSTLY redundant copper cable cable network in a kind of star configuration, for when everyone was still on copper.... Perhaps I could repurpose those cables! Hmmmmmmm.......food for thought! Smoke makes things work. When the smoke gets out, it stops! |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6781 |
I'm mot sure that these use a SMPS. They specifically specify 110-230V AC, 50-60Hz which makes me think there may be a mains transformer in there, possibly producing more than one voltage. Would the manufacturers clarify this, or even tell you if there's a DC supply option that could be retrofitted? I'm not sure about the consumption figure. They say 208mA but that's over 20W at 110V, not 15W. I'd use a 30VA reversed transformer if I was doing an inverter, I think, That's 74 dia x 31mm. There is a problem in finding a suitable power amp to run from 6V though. The lowest I've found so fat is 8V. That's a 30W bridged output. . Edited 2024-05-30 17:56 by Mixtel90 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: 4223 |
Why so difficult..? 60 euro UPS Volhout PicomiteVGA PETSCII ROBOTS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6781 |
Space, apparently. There isn't any. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
Attached is an image - sorry it is a little fuzzy, I will try to get a good photo tomorrow or something.  "P.max 15W"..... You could well be right - I don't have one to pull to bits here. I could order one to pull to bits. I think I will get management to cover the cost of that. If we COULD power the thing via batteries or Rob's idea of a LV copper AC to each box that we could then.... Naturally, anything like this kind of mod, would void any warranty.... Smoke makes things work. When the smoke gets out, it stops! |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
Well......this link is not English for a start!  Smoke makes things work. When the smoke gets out, it stops! |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6097 |
I can't work out the layout of your cabling but if you have one per residence, what happens if you simply bypass the unit that is being powered down. Jim VK7JH MMedit MMBasic Help |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2350 |
unlikely that they don't use a SMPS. to achieve operation at both 110v and 230v without any series/parallel switch at the primary requires you to oversize a normal 50/60Hz transformer such that it can: (a) operate at 230v without overheating, (b) at 110v still deliver sufficient voltage and current at the secondary. the end result is a transformer that needs to be several times bigger than would otherwise be needed. if followed by a linear regulator, that also needs to be oversized to handle the increased rectified voltage when there is 230v on the primary. the only device i've come across with such an arrangement is the Fluke 45 bench meter, that can handle something like 90v to 264v AC. Fluke use a buck converter after the mains transformer to cater to the wide (10-30v DC) rectified voltage range. for a discussion about replacing the transformer in a Fluke 45 see: https://www.eevblog.com/forum/repair/fluke-45-transfomer-foobar/msg5314255/#msg5314255 cheers, rob :-) addendum: from the datasheet and manufacturer's website, "The DTKom Series amplifiers incorporate a built in switched 110-230V AC power supply and are characterized by their exceptionally low power consumption for a long and trouble-free operating life", and, "Includes a high-performance low-power consumption switch-mode power supply". Edited 2024-05-30 18:41 by robert.rozee |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
What is the space ? The simplest and smallest UPS I can think of (assuming the Televes UPS will run at 120V DC also) is: 14 rechargable 9V batteries in series, charged from a 1N4007 diode from the mains in series with a relay coil of a 48Vdc relay and a resistor. In case the mains drops off, the relay wil switch the 120V from the batteries to the Televes while disconnecting the mains from it. When the mains returns, the charging restarts and televes is connected (relay back ON) to AC again. Maybe there is a more compact battery for 120Vdc , but the 9V where what I came up with. Volume of this would be roughly 16x 9V battery Run time would be roughly 80mAh x 120V / 15W = 9.6Wh/15W = 40 minutes. Volhout PicomiteVGA PETSCII ROBOTS |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
I just realize, You have a village network consisting of coax cable and launch amplifiers per house/few houses. And it is a chain coax network. When one of the houses is sold (uninhabitted) or renovated (turn power off temporary) the chain is broken, and half the village is without TV/Radio. But the launch amplifiers are powered from houses, correct ? Isn't it simple to power the launch amplifier from 2 houses. The chance both houses are renovating at the same time is low, and both houses uninhabitted at the same time also. A simple box, 2 mains cords, and the box has a DPDT mechanical relay to switch between the 2 power sources (switch both L and N). Volhout Edited 2024-05-30 20:58 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
It's funny you should mentin that - that is what is in place at a couple of locations, but we have been told by the power authority, that this is illegal, and must be removed. I/we wanted to do exactly that to every amp location, but when we approached the sparkies to look into doing it, it hit red-tape, and is actually illegal to do, so we can't do it like that, and we have to DISCONNECT the ones that have the dual-supply now to be compliant with the law. The issue is that it is illegal to use the power supply from one address, to power ANYTHING at another address. So while a dual 230v supply sounds ideal - and actually IS ideal - it is not legal, so we can't do that, unfortunately. As I say - once the power company found out that we had done that historically about twenty years ago at a few locations, they demanded that those hookups be disconnected immediately. So, we're stuck with UPS's at each amp location, or some other method of powering the amps at each location. I personally am rather liking Rob's idea of using a 48vAC central supply, and reusing the now mostly redundant grease-filled telephone cabling that pretty much runs everywhere, and definitely to every box with an amp on it, so getting a LV AC to every box from a central PSU via the phone cables would certainly be doable, but just weather we could get enough juice from that LV supply, to then power the amps is the question. Lots of things to think about, anyway! Smoke makes things work. When the smoke gets out, it stops! |
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