...Basic Bench Top Power Supplies

Wendy's Index

 

That is an awesome post ... seems I am not the only one to "dream big"

OK so to get me by for now ...

I have a few computer supplies and a few from games (I think X-box) .... all give 12 volts, no current control.

I just found a few boosters (dc-dc) fairly cheap: https://tinyurl.com/y5n4ea72

This would give me 24 volts at say 2 amps ... but no meter. I can put a meter in line but how can you tell what the limit is with no load?

Here is another booster with a meter ($20) ... https://tinyurl.com/yxb9j2ea

It has a meter built in ... though I can only read volts or amp at a time.

Can I just put one of these on my computer 12 volt supply and get a variable supply with a current limiter or ????

Any suggestions (I can get something better when I save up some money)???

Thanks so much for all the advice!!!!!

Mike

 

I hope you understand what you mean by current control. The PSU cannot control both current and voltage at the same time. You get one and not the other at the same time.

Treat the current and voltage settings on the PSU as limits.
If the voltage limit is reached before the current limit, you have a constant voltage supply.
If the current limit is reached before the voltage limit, you have a constant current supply.

 

I "think" I have it right ... honestly never had one before.

Lets see if I do:

Example 1) ... I want to charge a 12 volt battery at a rate of no more then 1 amp. I would set the amperage to 1.00 amps and then set the voltage to 12 (or 12.5 .. 13). This would charge the batter but at no more then 1 amp (if over time say 1 amp per hour).

Example 2) ... if I am playing with a motor ... and think I may have a short ... I could set my amperage to say 2.00 amps. Then set the voltage to say 6 volts ... try the motor. Normally it would push all the amps it could as it is a dead short and smoke. Now it will drive only 2 amps max so nothing burns up.

Do I have it right?

I just don't understand how the meter reads amperage with no load. I have a dc amp meter ... I put it inline with my load ... it only reads the actual load. How the heck will the meter on a supply read an amperage with no load?

Am I correct that I can put one of these boosters on a switching supply (like a computer supply)?

Thanks again .... Mike

 

1) A 12V lead acid battery needs about 14.5V to charge. 12V is not high enough to push 1A charge current.

2) An ammeter should read 0A with no load attached to the PSU. If you want to set the current limit, you have to apply a low-resistance load to the PSU. A properly designed CC PSU should allow you to short the output terminals without damage when you need to set the CC limit.

(I have seen some imported PSU that allows you to press the CC set button and then set the CC limit. This is an internal feature of the digital CC control and display. It does not do an actual draw on the PSU to verify this setting.)

 

That what I thought! I figured there had to some load to draw amps.

So, two questions still:

1) will these dc-dc boosters work with a switching supply feeding them?

2) will they double the voltage? If I put in 12, will I get out 24 ... or do they only boost say 50% max (so put in 12 get 18 out)????

Thanks so much again !!!!!!!!!!

Mike

 

This https://www.ebay.com/itm/DC-Convert...2A-Voltage-Voltmeter-Ammeter-Red/261244844928

guy here is pretty cute. I bought a couple and put them in a box to replace almost any wall wart.

You can set the current limit and voltage, so its both a CC and CV power supply.

There are all sorts of power supply types. CC is constant current, CL is current limiting. You can also have "foldback current limiting"

Take just about any standard adapter. 12 V most of the time and go a few volts less than 12. With a 24 V adapter in, you didn't get 24 unfortunately. You don't get zero Volts either. You can;t turn the display off either.

So in my case, there is a 5.5/2.1 and a 5.5/2.5 input jack with an adapt-a-plug out or a pigtail. Pick the right translucent case from hammnd and you can see the display. Polarity changes can be with the adapt-a-plug or switch the internal wiring. So, you need a wall wart to feed it.

I used on to replace a 6V adapter and never looked back.

Now for battery charging and plating. Charging needs a series diode. You might be better off with a stand-alone charger for the battery chemistry.

Plating is usually constant current. The argument against switching supplies for plating is probably the ripple magnatude. So if the ripple is 300 mV then it's plating and taking off and plating and taking off a small bit of material. So, it probably depends on what your plating, how and the voltages and currents involved.

 

It seems like others are considering purchasing all the parts new, that is almost always the most expensive way to go. Salvaged transformers from older equipment are a great find, if you can get them before those miserable copper-grubbers get them. One thing about plating is that with the nasty chemicals involved I would not put a good power supply any place near a plating project. Plating does not need the smooth regulated power, it can live with a bit of noise and hum.
So a separate power supply for plating is my suggestion. One reasonable source of bigger transformers is old battery chargers. Mostly what fails on chargers is the rectifiers, and mostly that is because they use the cheapest that can be found. The transformers may not always be pretty, but mostly they work. Of course the availability of discarded electronics varies a whole lot, depending on the area you reside in. Some places refuse to allow any salvage at all, enforced religiously by the local law enforcement. Other places are far more rational I have no clue as to where you are or the local policies in effect there, but good luck in salvaging.

 

It seems like others are considering purchasing all the parts new, that is almost always the most expensive way to go. Salvaged transformers from older equipment are a great find, if you can get them before those miserable copper-grubbers get them. One thing about plating is that with the nasty chemicals involved I would not put a good power supply any place near a plating project. Plating does not need the smooth regulated power, it can live with a bit of noise and hum.
So a separate power supply for plating is my suggestion. One reasonable source of bigger transformers is old battery chargers. Mostly what fails on chargers is the rectifiers, and mostly that is because they use the cheapest that can be found. The transformers may not always be pretty, but mostly they work. Of course the availability of discarded electronics varies a whole lot, depending on the area you reside in. Some places refuse to allow any salvage at all, enforced religiously by the local law enforcement. Other places are far more rational I have no clue as to where you are or the local policies in effect there, but good luck in salvaging.

 

You may want to entertain another option. Consider building your own power supplies to suit your needs. As you are already a collector of e-waste surplus electronics you may already have most of the components needed to build a fixed or variable voltage PSU for under $20. For a few additional dollars, you can add a digital panel meter for voltage and current readout.

This is an excellent idea, and there is a ubiquitous module on eBay and Amazon that offers some fancy adjustable voltage and current stuff, and it is cheap. You supply it with DC and it provides the UI and functionality. So, you’d just need a beefy DC source, the module, and a project box.

 

You guys are awesome!

Long story short .... I am just finishing a 5 year house building project (building the entire house accessible ... did as much of the work as I could myself). My wife was paralyzed from the shoulders down in a diving accident when she was 12 ... she is 40 now.

I almost forgot .... I am a pack rat and save everything .. when she got a new electric wheelchair, I am sure I saved the charger ... automatic but 24 volts, 10 amps ... and very heavy. I am sure it has a large 110 to 24 10A transformer in it! Everything is in storage in a tractor trailer parked right next to the house. I will have to dig through it and find it.

That should be a good starting point.

I do agree ... I don't want to spend $$$$$ and then take it into a dirty area. My shop is divided into areas ... clean (where I build electrical projects, use as an office, keep the compute and books), semi clean (machine shop ... some grease and oil but relatively clean) and dirty (actually a general area I use sometimes for welding, then sweep it up and use it for woodworking, clean it again and do some blacksmith work ... and push everything to the side and drive in a car to work on).

If I use this one for the charging and plating, I can use a switching supply for the electrical projects.

I will still need to come up with a heavy duty current and voltage controller for the 10A circuit. I know you can put too much power into plating and I would like to limit the charging amperage.

Thanks so much again!

Mike

 

You guys are awesome!

Long story short .... I am just finishing a 5 year house building project (building the entire house accessible ... did as much of the work as I could myself). My wife was paralyzed from the shoulders down in a diving accident when she was 12 ... she is 40 now.

I almost forgot .... I am a pack rat and save everything .. when she got a new electric wheelchair, I am sure I saved the charger ... automatic but 24 volts, 10 amps ... and very heavy. I am sure it has a large 110 to 24 10A transformer in it! Everything is in storage in a tractor trailer parked right next to the house. I will have to dig through it and find it.

That should be a good starting point.

I do agree ... I don't want to spend $$$$$ and then take it into a dirty area. My shop is divided into areas ... clean (where I build electrical projects, use as an office, keep the compute and books), semi clean (machine shop ... some grease and oil but relatively clean) and dirty (actually a general area I use sometimes for welding, then sweep it up and use it for woodworking, clean it again and do some blacksmith work ... and push everything to the side and drive in a car to work on).

If I use this one for the charging and plating, I can use a switching supply for the electrical projects.

I will still need to come up with a heavy duty current and voltage controller for the 10A circuit. I know you can put too much power into plating and I would like to limit the charging amperage.

Thanks so much again!

Mike

For na number of regulator circuits of many varied types, visit "schematics for free" website and go to the "power" directory. They have a lot of circuits there.