12V/24V outlets on your bench? - Page 1
Forum section: electronics / projects

author: nctnico
author_rank: Super Contributor
timestamp: May 02, 2020, 08:10:31 pm
content: A lot of circuits I design / work on run from 12V or 24V. When running these devices I usually use a power supply but since my bench is not so big a big bench PSU doesn't fit very well and there usually is a noisy fan inside as well.Now I got an idea: what if I made some boxes with 12V and 24V outlets (binding posts) with an on/off switch and locate these at strategic points I can do without the PSU(s). I'm wondering if anyone has tried this and whether it works well or not.

author: wizard69
author_rank: Super Contributor
timestamp: May 02, 2020, 08:31:17 pm
content: Quote from: nctnico on May 02, 2020, 08:10:31 pmI'm assuming you mean that the 12 or 24 VDC power supply is located off bench or at least out of the way. If so you can certainly do something in this respect and in fact you might be able to by something that comes close to fitting your needs. I'd look for ham radio / mobile radio power supplies and distribution systems. For example:https://powerwerx.com/powerpole-power-distributionwhich uses high current PowerPole connectors orhttps://www.amazon.com/MFJ-1104-4-Way-PowerPole-Distribution-block/dp/B00KC3G0MM. The biggest problem here is that they are designed for high current systems and don't usually come with switched outputs (at least not in low cost solutions). However you could certainly go the DIY approach, taking in proper safety considerations of course.As for the type of connectors to use that is up to you. For fixed voltage supplies it is probably a good idea to use different connectors. On top of all of that make sure you have components properly rated for the current levels involved.

author: Gyro
author_rank: Super Contributor
timestamp: May 02, 2020, 08:32:55 pm
content: It used to be common on school lab benches in times gone past. Individually fused and with a big central variable supply. Brough out on 4mm binding posts.If you're going to do something like that, maybe for semi-permanent stuff too, then you could maybe standardised low cost connector, maybe a 4 pole Speakon connector, that would give you access to 12V, 24V, (and maybe 5V?) on separate pins of a single outlet. That would reduce the risk of mis-connection.Your biggest problem might be providing overcurrent protection for individual outlets.EDIT: Sounds like great minds....

author: ogden
author_rank: Super Contributor
timestamp: May 02, 2020, 08:33:37 pm
content: If you findyour ideauseful then go for it. When I had to work with powerful 12V stuff, I got big system supply, put it next to the table, run fat cable with remote sense into working area. Did not need a switch because one hi-power connector and on/off button on the supply for me worked well. You may need many terminals, each with separate switch and that's fine (in your case).

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 02, 2020, 10:31:09 pm
content: How much current? If only a little, get a wall wart and secure the cable to prevent it from falling behind the bench. If a lot, PC PSUs (especially the server kind) are very compact for the power output.

author: John B
author_rank: Frequent Contributor
timestamp: May 02, 2020, 11:24:40 pm
content: What about a post regulator in the smallest form factor you can? Something like those Riden(?) supplies. All the AC/DC conversion can be in a larger unit that's tucked away, then have a small supply that is close to your circuit and still has good voltage and current regulation.

author: nctnico
author_rank: Super Contributor
timestamp: May 03, 2020, 01:31:45 am
content: I see some good suggestions and food for thought. Current limiting is a good one but I don't like fuses. The amount of current is about 2A max. Wall warts could be an option too; it's just that I have standarised on 4mm banana leads but it's not a problem to attach a small box with binding posts at the end of a wall-wart (and I have oodles of mains outlets anyway). I like the idea of the Riden modules as well. Gives more flexibility both in voltage and current limiting. Noise and precise voltage aren't an issue anyway.

author: bob91343
author_rank: Super Contributor
timestamp: May 03, 2020, 05:58:38 am
content: If a regulated power supply is at a remote point, one must take into account the resistance of the interconnection. Many good power supplies have remote sense capability, which is what's called for here. If the resistance of the leads is only one Ohm and you are drawing one Ampere, you lose one Volt. When you lighten the load, you regain some of it. So the regulation is ruined by the cable.A remote sense system measures the voltage at the load and adjusts the source to hold it constant.An alternative might be to use very heavy cable but that's expensive, hard to manage, and rather than solve a problem just amelioreates it.On the other hand, remote sensing courts instability, depending on the details.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 04, 2020, 01:41:17 am
content: Quote from: bob91343 on May 03, 2020, 05:58:38 amSo true ... it depend if you have a resistive capacitive or inductive load, i have a Kepco psu with remote senses, and big inductive load make the psu go crazyMost of the times i use computer atx psus, i have foud some Dell psu who work very well, very good regulation short protection over voltage etc ..., only a mere 20$ usd purchase, never had problems, added some banana jacks.For protection you could use polyswitch fuses (auto resettables fuses) make somekind of rotary switch box with many / different current values ??

author: james_s
author_rank: Super Contributor
timestamp: May 04, 2020, 03:35:09 am
content: When I need 12V with a good amount of current I use a server PSU. I have some IBM branded ones that are very slender, almost silent and good for 675W. I modified a pair of them for series operation by isolating the DC ground from earth and use that to power my LiPo chargers.

author: Someone
author_rank: Super Contributor
timestamp: May 04, 2020, 07:50:50 am
content: Quote from: Gyro on May 02, 2020, 08:32:55 pmHave also seen this in production, and MRO of different organisations. Running low voltage soldering irons directly off the outlets was convenient.

author: tszaboo
author_rank: Super Contributor
timestamp: May 04, 2020, 07:57:02 am
content: I had this in my old workplace. 8 workplaces, with power output, bench lighting, shelf above the table, all built from those aluminium frames. Excellent as a bench. It had a power output, nobody ever used it. Maybe if you DIY it, label it correctly, and you are the only person who is ever expected to use it, maybe.

author: olkipukki
author_rank: Frequent Contributor
timestamp: May 04, 2020, 08:07:00 am
content: Quote from: nctnico on May 02, 2020, 08:10:31 pmI have been in same boat too, and after pros & cons - my choice in urban planning approach, where a land is limited and very expensive, and only way to build vertically.Aa result, I build an extension from aluminium extrusion profiles that fit "gadgets" nicely in a very confined area. The thing is over 2 meters and taken 350x500 (WxD) mm footprint. The first PSU is leveled as a table height and since a depth is smaller than my bench table, so can access these easy. Also, got extra storage below and above usable space.

author: nctnico
author_rank: Super Contributor
timestamp: November 08, 2020, 07:18:09 pm
content: Final verdict:After some pondering and calculations on time/money I decided to buy a bunch of Gophert NPS-1602 60V 3A power supplies (*). My need basically comes down to having a bunch of adjustable wall-warts and the units from Gophert fit the bill nicely. Teardown videos show good behaviour on the current models. So far I have received 1 (out of 3) and it seems to work. It is even smaller than I expected and no noise since it doesn't have a fan. The last setting is stored so no re-adjusting the output voltage between shutdowns. The inside looks surprisingly organised but I did replace the toy-ish binding posts with higher quality ones.* Actually this is isn't entirely true. I ordered 3 units from a different company called Rek which produces very similar looking PSUs (with the outputs on the back) but it seems the package got lost. I decided to go for Gophert units instead; in the end having the binding posts on the front seemed like a better usage of space than having the power displayed all the time.

author: olkipukki
author_rank: Frequent Contributor
timestamp: November 08, 2020, 08:35:53 pm
content: Actually, nobody mentioned DIN rails PSU.Is not practical or too much $?As a space saver, it's deal for me to have couple dedicated Meanwell SDR 48V on the bench eventually. Still need to organise this...

author: nctnico
author_rank: Super Contributor
timestamp: November 08, 2020, 10:35:54 pm
content: Quote from: olkipukki on November 08, 2020, 08:35:53 pmSafety is an issue with the open screw terminals but I like a current limit and to see the consumed power as well. In the end an adjustable power supply is a bit more versatile (although I know I started with 12V and 24V).

author: ogden
author_rank: Super Contributor
timestamp: November 09, 2020, 05:44:56 pm
content: Quote from: olkipukki on November 08, 2020, 08:35:53 pmThat's because DIN rail PSU's are good for (surprise surprise) DIN rails. Answer to question of fixed voltage supply on your bench depends on your specialization *and* depth of your pockets and kinda size of your lab as well. If you are specialized in electronics that requires xx Volts *and* loads of watts, but can't afford powerful lab supply - buy xx Volts fixed supply. It definitely will be cheaper and will take less space. In general that's it. Kinda obvious advice Fixed supplies do not have CC mode, but in repair/design work it is often needed for various reasons.

author: ejeffrey
author_rank: Super Contributor
timestamp: November 10, 2020, 05:33:17 pm
content: Quote from: bob91343 on May 03, 2020, 05:58:38 amMaybe you have a different impression of the OPs goal but I assume the idea is to put the power supply near the bench in the same room at least. 1 ohm would be a huge resistance in this sort of application. 16 gauge wire is 4 ohms per 1000 feet. That would mean a 100 foot run would still have less than 1 ohm including both conductors. Unless your power supply in several rooms away or you are using really undersized wire you will be more likely to have < 200 mOhm.Remote sense isn't a bad idea but is likely not actually needed for a 12 or 24 V supply. Motors and heaters won't care and most anything else you run from those voltages have internal regulated power supplies.