Benchtop Power Supply Question

[stj]

Re: Benchtop Power Supply Question

the chinese breakers are probably "B" grade.
there are 3 or 4 speed-grades - B is often used like you say for motors and other high-inrush stuff.
you need "B" for a lot of the battery-tab spot welders!

btw, a fuse or breaker should stay intact at 100% current indefinatly.

[redwire]

Re: Benchtop Power Supply Question

I have an LED energy meter DIN panel mount like https://www.aliexpress.com/item/10000138101252.html
But I don't like it because it has such slow averaging, it takes 3-4 seconds to ramp up to its power reading. I guess that's OK for fluctuating loads. Otherwise it works really well.

Ali DIN-rail circuit breakers looked a bit hokey - they seem to need 3X rated to trip fast, never mind they have no safety approvals. They seem suited to motors etc. I would want a fast trip on a workbench, so I think a glass fuse is best.
edit: In North America we don't use DIN-rail for the service/consumer unit panel, and those breakers look really slow.

Others I look at and have used:
Tyco W58 series (thermal) but 0.5-3.4 sec fastest response at 1,000% rated current.
Tyco W28 series (thermal) but 0.12-0.3 sec fastest response at 1,000% rated current.

[stj]

Re: Benchtop Power Supply Question

i have this:
https://www.aliexpress.com/item/1005002687372957.html
the oldskool LED version.

although the lcd one is a tempting upgrade

[stj]

Re: Benchtop Power Supply Question

it doesnt,
an iso transformer can kill you as easy as mains
they are to isolate the device from ground for your scope.

[eccerr0r]

Re: Benchtop Power Supply Question

I really should look into getting one of those cc current/voltmeters, been using my P3 Kill-A-Watt for that purpose but I only have one of them and would like to keep it for measuring real watts (versus VA which is more interesting for debug in general)...

Alas I just use an isolation transformer, though I should just use an RCD/GFCI near my work area. Alas as of now, I think every time I had a GFCI trip, it was a nuisance trip

As for the isolation transformer, I get no indication when it saves my life...

[stj]

Re: Benchtop Power Supply Question

i have a din rail box containing an rcd, a breaker and a chinese volt/current meter with a socket on the outside

[redwire]

Re: Benchtop Power Supply Question

The GFCI basic circuit allows you to change sensitivity but the hassle is that latching relay in one. I could not find one to buy separately.
Also, the CT's are really good 1000 turn can be used for measuring low AC currents.

I just took a Leviton GFCI stuffed it in a metal box with line cord and that is an inline GFCI I added to the workbench. I have no DIN-rail stuff.
It's a good reminder I need to add a fuse to it as well. I don't need 15A surprises and even a 5A fuse is good for whatever I am repairing.
I might look at an arc fault circuit interrupter (AFCI) but so far these are all only available as breakers, not outlets.

[Per Hansson]

Re: Benchtop Power Supply Question

How would you do this can you please give an example of a circuit for one because I would like to make one for my work bench

What redwire was implying is you can modify them to be more sensitive.
Not a good idea to be tinkering with such devices and possibly introducing errors.
I would not recommend to build one yourself, they are cheap enough brand new and are designed to save your life if you fuck up too badly.

[jiroy]

Re: Benchtop Power Supply Question

an RCD, good but not foolproof.
it works by balancing an arm between 2 coils - if one side has more current than the other then the arm moves and it trips.
i think the newer ones overcomplicate things using a 3rd coil and an opamp to trip a solenoid

if you connect a transformer to the line the RCD cant see what happens on the secondary side.
in short - you can kill yourself if you get careless with an isolation transformer!

Good points ; Electricity and Electronics aren't something to take lightly , and I always wondered if someone put some reminders each thread or so . Beginners and hobyists must always be aware of safety and security measures . If we add a case of spilled water or naked feet , it could be a recipe of disasters .
Even a variac or an isolated transformer won't protect you from a big capacitor's lethal discharge . Even a 19 volts secondary circuitry can hold a potential danger .
That's said , I had this idea since the table is in the room's center and future probable cables will pass on ground , so the RCCB is placed now in the lead casing of the room's circuitry .

[stj]

Re: Benchtop Power Supply Question

Big Clive has reverse engineered a couple on his YT channel

[sam_sam_sam]

Re: Benchtop Power Supply Question

You can also find GFCI's in the trash, take them apart and you could make a custom one.

How would you do this can you please give an example of a circuit for one because I would like to make one for my work bench

[redwire]

Re: Benchtop Power Supply Question

I added a GFCI outlet to my workbench power and it's tripped once, paid for itself.
I wasn't using an isolation transformer (what is everyone rich?) and had line/neutral flipped on the alligator clips doing some live stuff. A small spark and that's all.
In North America these are electronic, use a CT and trip at >4-6mA imbalance and activate the latching relay. Not the hairdryer crap mechanical ones.
You can also find GFCI's in the trash, take them apart and modify. Although they frequently are blown inside, you could make a custom one.

Modern complicated circuit TI AFE3010 but I like the old orginal LM1851 DIP-8.

Old GFCI's get hit with mains transients, MOV's fade out.
I had one GFCI trip but the relay jammed and power stayed on and the coil+SCR burned up badly. It latches power to the coil which is fine for a short time to trip.

[stj]

Re: Benchtop Power Supply Question

an RCD, good but not foolproof.
it works by balancing an arm between 2 coils - if one side has more current than the other then the arm moves and it trips.
i think the newer ones overcomplicate things using a 3rd coil and an opamp to trip a solenoid

if you connect a transformer to the line the RCD cant see what happens on the secondary side.
in short - you can kill yourself if you get careless with an isolation transformer!

[jiroy]

Re: Benchtop Power Supply Question

That's the anti-electro i talked about previously :

RESIDUAL CURRENT CIRCUIT BREAKER (RCCB)

Device installed in the distribution board upstream of the electrical circuits, this detects current leaks due to insulation faults and prevents any risk of electrocution by immediately cutting the power to the circuit concerned. A switch handle is used to reset it after the fault has been eliminated.

[jiroy]

Re: Benchtop Power Supply Question

So far , I've finished the over-voltage timer , and looking to start designing the main board .
Till now I've decided on one winding DC part (low AC) with one tapped center , despite that two windings are better for noise and easier repair . Anyway , I won't wind it until I finished designing the whole circuit , including protection ones . It's the preferred method anyway to work it in reverse , since it will be decisive in core's calculation .
Right now , I'm studying the different options of diodes or rectifiers ..Attached some of the primary ideas , but nothing decisive yet ..

[JC173]

Re: Benchtop Power Supply Question

Thanks dude ; I was worried if you feel your thread was hijacked ..

Nope, not at all. It's all great info I'll use somewhere

[sam_sam_sam]

Re: Benchtop Power Supply Question

Those are never used parts from new not used devices , most of them given as bonuses on quantities sales or left overs defaults , or stocks . Those are surely the 0,001% of my arsenal , the ones that I didn't have time to arrange in their accordingly drawers and left on purpose at home for quick repairs .

If you were a projects designer , you would know that those are for repairs mainly , and more important , a precaution measure against an obsolete part . When I want to do a project , I prefer ordering a complete kit , like this one attached , mainly for time saving more than money saving . This kit was delivered 2 days ago .

Interesting

[jiroy]

Re: Benchtop Power Supply Question

I'm always pleased to learn way more than the simple answer to a question. These comments are great.

Thanks dude ; I was worried if you feel your thread was hijacked ..

[jiroy]

Re: Benchtop Power Supply Question

WOW How often do you used these reclaimed parts in your projects

Those are never used parts from new not used devices , most of them given as bonuses on quantities sales or left overs defaults , or stocks . Those are surely the 0,001% of my arsenal , the ones that I didn't have time to arrange in their accordingly drawers and left on purpose at home for quick repairs .

If you were a projects designer , you would know that those are for repairs mainly , and more important , a precaution measure against an obsolete part . When I want to do a project , I prefer ordering a complete kit , like this one attached , mainly for time saving more than money saving . This kit was delivered 2 days ago .

[JC173]

Re: Benchtop Power Supply Question

I'm always pleased to learn way more than the simple answer to a question. These comments are great.