Power supplies, UPS and surge protection
A camera "disappears" every evening around ten and is back by morning. The recorder reboots once a week, always at night. After a thunderstorm three cameras out of eight do not respond and the rest work fine. Behind all three is the power, not the camera. These are also the most tedious faults to track down, because the device itself is healthy — it simply is not getting what it needs.
1. Choosing a power supply — three numbers and one margin
A power supply has three figures: voltage (must be exactly right), current (must be at least what is needed) and stability (must hold the voltage under load as well).
| Voltage | Where it is used |
|---|---|
| 12 V DC | By far the most common: IP and analogue cameras, sensors, locks, small monitors |
| 24 V AC | Some PTZ cameras and heated housings. Not the same as 24 V DC — the wrong type destroys the device |
| 48 V DC | PoE injectors and switches |
| 5 V / 9 V | Small devices, routers, modules |
Regulated or not
A regulated supply holds the voltage steady regardless of load. A cheap unregulated one gives 13–14 V with no load and drops to 10 V under load — the camera works during the day and reboots at night. All our camera power supplies are regulated; this is not the place to save money.
2. The most common fault: voltage drop in the cable
This deserves its own section, because most of the "strange" faults come from here.
12 V power is run to the camera on a thin two-core cable. The cable has resistance. The longer and thinner the cable and the higher the current, the more voltage is lost on the way. At the camera there is no longer 12 V, but 10.5 V.
Example: the camera works by day and disappears at night
The camera draws 3 W by day and 9 W at night with IR illumination. The power cable is 40 m and thin. By day there is just barely enough voltage, at night there is not — the current triples and the voltage drop with it. The camera reboots, the IR goes out, the voltage recovers, the camera starts, the IR comes on — and so on all night.
Three solutions: a thicker cable, the power supply close to the camera (not in the cabinet), or the simplest one — PoE, where at 48 V the current for the same power is four times lower and the voltage drop therefore negligible.
3. Central power or local power
| Central, from the cabinet | Power supply on the spot | |
|---|---|---|
| Pros | One place to maintain, easy to put behind a UPS, one surge protector | Short cable, no voltage drop, inexpensive |
| Cons | Voltage drop, thicker cable | Every supply is its own point of failure, hard to put behind a UPS, 230 V has to be brought to every point |
| When | A compact site where you want everything in one place | A spread-out site where 230 V is there anyway |
For central power we have DIN-rail supplies (12 V 2 A up to 10 A) and lockable metal enclosures with a tamper switch, with room for the supply, a battery and distribution. For local power there are supplies in IP65/IP67 enclosures, some of which fit straight inside a junction box or a camera mounting base.
4. UPS — what you are actually paying for
A UPS is not only for "the power went out". Most of its value is against short disturbances: sags that make the recorder reboot, and fluctuations that kill hard drives. A recorder rebooting in the middle of a recording can corrupt exactly the file you will need later.
VA and W are not the same thing
The big number on the box is in VA, but load is counted in watts. A 600 VA UPS gives about 360 W, a 2000 VA one about 1200 W. Always calculate in watts and leave margin — a UPS running at full load gives you runtime in minutes, not tens of minutes.
| Type | What it does | When |
|---|---|---|
| Line-interactive (AVR) | Corrects the voltage itself, switches to battery within milliseconds | The default choice for a recorder and a switch. Most of our UPS units are these. |
| Online (double conversion) | Power always comes from the battery, the mains only charges it — there is no break at all | Server room, critical site, poor mains supply |
| 12 V DC UPS | Buffer power straight to the camera, without 230 V | A single camera or gate, where a 230 V UPS would be overkill |
We have models for DIN rail and 19" racks as well as desktop units; the larger ones have a USB interface, which lets the recorder shut itself down properly when the UPS says so, instead of dropping out abruptly when the battery runs flat.
5. Surge protection — the lightning does not have to hit you
It is commonly assumed that a surge means a direct lightning strike. In practice induction is overwhelmingly more common: the strike hits something a few hundred metres away and a long cable acts as an antenna. The induced pulse is short, but enough to take out a camera's network interface or a recorder's port.
That is why long outdoor runs are the most vulnerable — exactly the ones a surveillance system always has.
Where to protect
| Line | Why |
|---|---|
| 230 V input | In the cabinet, ahead of the whole system. A DIN-rail protector. |
| Ethernet / PoE | The most important point in a surveillance system: the cable goes outdoors and brings the pulse straight into the switch. The protector passes PoE power through. |
| 12 V / 24 V power line | When power is run a long way on a separate cable |
| Video (BNC) | In analogue systems |
| RS485 | PTZ control, long data lines |
6. Connections — do them properly, every time
Most later call-outs come not from the equipment but from the joints. Twisted-together conductors and insulating tape work flawlessly on installation day. The problem arrives a month or a year later, and by then it is hidden.
- Always use the connector meant for the job. A screw-terminal 2.1 mm plug for power, a proper RJ45 for the network. We have both ordinary and pass-through (EZ) plugs — with a pass-through plug the conductors are visible before crimping, which cuts the risk of the wrong order considerably.
- Do not join a cable by twisting. For joining network cable there is a junction box with krone terminals: the conductors are pressed into the terminal, the joint is gas-tight and measurable. A twisted joint gives you an intermittent fault that is almost impossible to find.
- Crimp with the right tool. An RJ45 squeezed with pliers may pass the tester and come apart six months later.
- Test before you close everything up. A line put through a tester is cheaper than getting the ladder out a second time.
7. Outdoors — where connections really fail
The Estonian climate does three things to a joint: moisture, freezing and UV from the sun. All three work slowly and unnoticed.
Rules that prevent most call-outs
- No joint may hang in the air or lie on the ground. A joint belongs in an enclosure: a junction box, a camera mounting base or a protective enclosure.
- Use weatherproof joint sleeves. A sleeve with gel or a seal genuinely closes off the area around the conductors. We have them for 3- and 4-core cable, for T-branches, and a separate IP67 sleeve for RJ45.
- Insulating tape is not waterproofing. It gives up in the first winter: the adhesive dries, the edge lifts and water runs in along the cable.
- Make a drip loop. Take the cable below the joint first and only then up — water runs along the cable and drips off the bottom of the loop instead of into the enclosure.
- The cable must be rated for outdoor use. The sheath of an indoor cable cracks in UV within a couple of seasons.
- Put the power supply in an enclosure, not loose. We have IP65/IP67 supplies that fit inside a junction box or a camera base — that way there is no separate "wet spot" at all.
The camera's own connection
Most cameras have a factory pigtail with a short RJ45 end. That end must not be left loose against the wall: it goes either inside the mounting base (the cleanest way) or into an IP67 sleeve. For door stations and cameras mounted directly on a façade there are rain shields — these are not for looks, they keep water away from the seal.
Summary
- Voltage exactly right, current with 30% margin — and 24 V AC is not 24 V DC.
- 12 V does not like a long cable — beyond 20–25 m bring the supply to the spot or use PoE.
- The whole chain behind the UPS — recorder, switch and router, not just the recorder.
- Surge protection at both ends, with the earth connected — without earth it does not work.
- Always a connector and a terminal, never twisted conductors — and every outdoor joint in an enclosure, with a sleeve and a drip loop.
Power supplies Accessories and connectors PoE power supplies
Power and network together are covered in "Power and network on site". If in doubt, get in touch — we will go through the load and the distances with you.
Exact figures for each product are on its own product page. For installation and earthing requirements, always follow the electrical installation regulations in force and the device's own installation manual.