5 volt regulated Supply

Gramps

Senior Member
Looking for a source for a really decent plug-in regulated 5 volt power supply.
Among the thousands of online parts, what are you long time "Picaxe Pros" using?
A unit that would work for breadboarding and for finished projects would be great. We don't mind paying a little more for quality!
Thanks, Gramps
 

datasmith

Well-known member
I bought this from Amazon.com for $40 US last September.
It's just 2AMPS but plenty to breadboard micro-controller circuits and small servos, etc...
Adjustable voltages include 5V, 9V and 12V among others. This allows me to test my voltage regulated circuit designs against 9V and 12V battery sources.
Small, light weight, clean voltages. It's been working great for me non stop since I purchased it.

Battery Eliminator, Power Supply, AC to DC, 3V, 5V, 6V, 7.5V, 9V, 12V Outputs 2 AMPS Regulated DC Power
 

lbenson

Senior Member
really decent plug-in regulated 5 volt power supply
Not sure exactly what you mean. If a bench power supply, then the suggestions above could work for you, especially Tex's if you are looking for current limiting to guard against shorts in your projects under development (though you're not likely to want to use it for finished projects, especially if they're going somewhere away from your bench).

If you're just looking for a beefy plug-in, I've been using these 2A and 3A units:

 

techElder

Well-known member
and for finished projects
Sorry, Gramps, I didn't retain that you were looking for something to go with a finished project.

Like you said, there are so many options. Lance's choices certainly would be adequate for normal low-power projects and development. I also use something like that to power my development platform (AXE091.)

You definately should look for "universal" input voltage (90 - 240 vac) units, although the mechanically different plug situation is usually ignored.

Mostly, I'm building to fit protected 18650 batteries with external recharge capability. Seems like the way to go anymore.
 

datasmith

Well-known member
Sorry Gramps. I read that wrong too. Didn't catch that you wanted a supply that you could also use for the finished project. I'm typically building battery powered projects. Ergo I need a true bench supply.
 

lbenson

Senior Member
Do you have a source for these batteries and their charger.?
Here is my latest for nearly-off-the-shelf 18650 battery holder + charger UPS:
18650 UPS A.jpg
Like this: https://www.aliexpress.com/item/4000200690185.html
As this youtube video points out, there's an issue with these if used as a ups--if mains gives out and the battery is discharged, if the load upon the return of power exceeds a certain, small, amount, the battery won't recharge:
I've made the following modifications to get around this problem:
18650 UPS B.jpg
As shown in the photo, I cut the trace between the ON switch pin and the V+ pin on the usb connector and replaced that link with a 1N5818 schottky diode. I ran a wire from the diode near the USB charging connector (S1) to another 1N5818 also connected to the same V+ pin. If mains comes back on when the battery has been discharged, the mains current supplies the load with (assuming not too great a load current) a surplus to charge the battery.

This has not been extensively tested, but seems to work--if your circuit can tolerate a little less than 5V because of the schottky diode voltage drop.

These are available with slots for 1, 2, or 4 18650 batteries. Runtime on battery will depend on how good your batteries are. I always use "protected" 18650 batteries because of various dangers. These battery chargers are also quoted as having battery protection. Belts and suspenders, I hope.
 
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hippy

Senior Member
Looking for a source for a really decent plug-in regulated 5 volt power supply.
It really depends on what you consider "decent" and what specification you are after. For 5V would normally just grab a USB power supply, measure it's voltage to check it's within a reasonable 5V spec.

USB supplies are usually very generic so hard to recommend any particular brand but anything which is used with high-quality kit should be good enough. The higher the current rating the more likely it is to have a better spec in my experience.

For breadboard work I would always use a bench supply which has current limiting.
 

rq3

Senior Member
I've purchased this model (have two for various reasons) and have been satisfied with their load carrying and sufficient regulation. I don't remember who recommended them to me, but someone did.

I bought the 30A version.

I see that they are not in stock, but perhaps you could do a search for other suppliers.

30V 10A/5A DC Power Supply Adjustable Variable Dual LED Display Digital Lab Test
I have what looks like a 30 volt/30 amp (1 KW) supply from the same manufacturer. They're all over the Bay, and seem to work pretty well. I've had mine for years, and it works well for everything from micro-welding, to massive lead-acid battery charging, to electroplating and anodizing, to powering breadboards. But it's one of dozens of supplies I drag out (or build) and use depending upon need.

A few provisos:
1) Mine is VERY slow to respond. It even takes several seconds to power on, or off.
2) The constant current, or current limiting, function, is very strange. Not unusable, but takes getting used to. As a retired Hewlett-Packard engineer, I find having to short the supply to set the current limit a tad...odd. It's reliable and functional, but...odd. Regulation is acceptable. Not great, but acceptable. Noise is good per wideband oscilloscope, and stability is good.

Overall, a good supply for the price. Just be aware that you will get what you pay for.
 
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lbenson

Senior Member
How much would you limit the current when working with micros?
Whether to even bother depends to a considerable degree on how much you have to lose. You can burn out a picaxe pin with, say, 30mA. Or a chip with 100mA or less. If you're attached to $50 worth of gear which can be damaged, perhaps you'd choose to use a current-limiting supply. If you're controlling industrial equipment, surely you should.

To answer the question of how much, you'd need to know how much of a load you would expect given the conditions you want to operate under.
 

Gramps

Senior Member
I have a 28X2 That has a burned-out pin. We were quite surprised to see that the rest of the chip still works fine. Don't know how we did it. Would running a load on a pin without a resistor smoke it?
 

premelec

Senior Member
Yes - have you ever seen pictures of the tiny wires that connect pins to chip? Like a 30ma fuse wire!
 

lbenson

Senior Member
Would running a load on a pin without a resistor smoke it?
If you change "would" to "could", the answer would be "Yes, definitely".
Suggestions are to not exceed about 20mA on a picaxe pin (maybe 25mA--exact limits to be found in the microchip documentation). If you hook an LED to a picaxe pin without a resistor, you will probably burn out the pin.
 

hippy

Senior Member
How much would you limit the current when working with micros?
When running an AXE091 board to test programs I usually run at 3V3 and about 35mA. That gets wound up as appropriate when additional hardware gets connected.
 

Gramps

Senior Member
So basically use a wall wart for finished projects and a current limiting power supply for experimental work. That makes good sense.
 

Gramps

Senior Member
This from Adafruit Industries
LED
current use is measured in milliamps (mA). As a rule of thumb, we usually use 20 mA as a guideline for a single LED at full brightness, and each color “pixel” contains three LEDs (one each for red, green and blue), for a total of 60 mA per pixel when displaying white at full brightness.
 

premelec

Senior Member
FWIW I use a module from Ebay that shows and regulates voltage and current - a step down regulator that I attached to an old HP 30V 2A switching
power unit - the module I got was 30v 4 amp so can produce up to 12v 4 amps out - for example of the units I'm referring to: search DC32V/3A DPS3003 DP20V2A 30V5A on Ebay - I'll try post a photo later. I also use a 2x lithium battery case with switch - use only one battery and put an up converter in the other battery compartment to set 5 to 12 volts out [with 1 amp battery over discharge protection bit].
 
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Hemi345

Senior Member
FWIW I use a module from Ebay that shows and regulates voltage and current - a step down regulator that I attached to an old HP 30V 2A switching
power unit - the module I got was 30v 2 amp so can produce up to 12v 4 amps out - for example of the units I'm referring to: search DC32V/3A DPS3003 DP20V2A 30V5A on Ebay - I'll try post a photo later. I also use a 2x lithium battery case with switch - use only one battery and put an up converter in the other battery compartment to set 5 to 12 volts out [with 1 amp battery over discharge protection bit].
I was just going to ask if anyone had used one of the RD Tech power supplies and could recommend one. I've had the DPH5005 in my Ebay cart for months. They have software that allows you to use your computer to connect to it with either USB or bluetooth (if you get a model that has those capabilities). I downloaded and played around with the software a while back and it seemed very mature and easy to use. The logging function is pretty neat too. I'll order one when I finish up some of these other non-electronic projects hopefully in the next couple months 🙃
 

premelec

Senior Member
@Hemi345 - that looks similar to what I've been using - just at higher price - there are units as low as $12 if you can deal with monocolor screen... The one 'complaint' I have is that I forget just how the multi function clicks work - not simple twist of knobs like on my old Heathkit CC CV supply - anyhow once you get used to how the controls work they work quite well and the unit is pretty efficient... the higher current ones may need a fan on their heat sinks running higher currents - I bought my 35v 4 a unit for about $25. a few years ago.

The unit is a bit small but quite readable... I've also attached a picture of the 2 x Li Battery case used with up converter on one side - in this instance producing 8 volts or so for a component test module - can also be adjusted for 5v or 12 v... [see post 25 above]
 

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lbenson

Senior Member
This from Adafruit Industries
LED
current use is measured in milliamps (mA). As a rule of thumb, we usually use 20 mA as a guideline for a single LED at full brightness
20mA may be full brightness for an ordinary high-brightness LED, but the LED is not self-limiting. At 5V, you would need about a 220 ohm resistor to limit the current to a bit more than 20mA. (5V/220R = .0227A).

The Adafruit Industries document https://learn.adafruit.com/all-about-leds/what-are-leds-used-for also says this about using a "zero ohm resistor (also known as a wire)":, "Warning! Spoiler! This following experiment will probably destroy your LED". But if you're providing power to the LED directly through the (non-limiting) picaxe pin, you will probably burn out the pin first.

"The lesson? There are limits to how much voltage and resistance, if we go over the limits, the LED will die!" [From Adafruit Industries]
 
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Hemi345

Senior Member
@Hemi345 - that looks similar to what I've been using - just at higher price - there are units as low as $12 if you can deal with monocolor screen... The one 'complaint' I have is that I forget just how the multi function clicks work - not simple twist of knobs like on my old Heathkit CC CV supply - anyhow once you get used to how the controls work they work quite well and the unit is pretty efficient... the higher current ones may need a fan on their heat sinks running higher currents - I bought my 35v 4 a unit for about $25. a few years ago.
The DP"H" models are buck-boost where as the DPS are just buck. I was thinking I'd do like you and use a quality laptop PSU I have laying around to power it. Check your model to see if it has the little 4 pin header for USB or BT connection. The software would help make using it easier than the little display and buttons.
 

erco

Senior Member
TTYTT I have yet to see a blown Picaxe output pin from an LED without a resistor. In my classes, students regularly leave out the resistor and everything still works, even after several hours of constant use. I'm not recommending this practice, just pointing out that Picaxes are pretty durable. Pretty sure I measured the current a while back, and it was ~25 mA sans resistor on a red LED. The Picaxe pins' internal resistance helps out.
 

johnlong

Senior Member
Hi
I use mobile phone chargers cheep to pick up at markets or car boots
cut the end off and solder male jumper wire ends to them good for bread boards
or sticking into female headers
 

lbenson

Senior Member
TTYTT I have yet to see a blown Picaxe output pin from an LED without a resistor. In my classes, students regularly leave out the resistor and everything still works, even after several hours of constant use. I'm not recommending this practice, just pointing out that Picaxes are pretty durable. Pretty sure I measured the current a while back, and it was ~25 mA sans resistor on a red LED. The Picaxe pins' internal resistance helps out.
Well whaddaya know. I didn't want to risk a 14M2, but I have a supply of 14Ms from years back, so I hooked up orange, yellow, bright green, purple, white, and blue LEDs directly to pins B.0-B.5. A program which cycles through them one at a time for a minute each shows no problems so far, and flashing all of them simultaneously also works. This is with a 5V supply.
 

hippy

Senior Member
A program which cycles through them one at a time for a minute each shows no problems so far
"So far" might be the pertinent part of that. Running any LED without a resistor is definitely not something which is recommended and not something to get into the habit of doing.

PICAXE output pins can be robust, can stand a fair bit of abuse, but they don't always survive abuse or last forever when being abused.
 

premelec

Senior Member
I was just wondering if the 5v supply might be a bit soft or current limiting - have you measured actual voltage/current on the PICAXE pins?
 

hippy

Senior Member
I believe it is more that the PICAXE outputs are somewhat current limiting. In the 08M2 Microchip Data Sheet - and maybe others - there are a set of graphs which show VOH vs. IOH and VOL vs. IOL graphs at various voltages. Figure 31-41 onwards in the datasheet I have.

For driving something from an output connected to 0V, 'turned on when output high': As the current drawn from an output increases the output voltage drops. Which is effectively current limiting.

But as output voltage drops then more voltage is being dropped in the high-side switch which, with the same current passing through that, causes more heat. This is what has the potential for damage.
 

Hemi345

Senior Member
Lance, since you're in "Destructo Mode" ;), try tying the anode of the LED to V+ and let the PICAXE sink the current. Does either the LED or PICAXE pin survive? I haven't had a chance to look at the datasheets Hippy recommended but quite a few ICs I've used state they can sink more current than they can source, so just wondering how this behaves (not that I'll eliminate the resistor any time soon, just more for curiosity's sake).
 

AllyCat

Senior Member
Hi,

Beware that not all PIC(axe) families are the same, so a test on an 08M will not necessarily predict how an 08M2 might behave (or vice versa).
....try tying the anode of the LED to V+ and let the PICAXE sink the current. Does either the LED or PICAXE pin survive?
Possibly not, because the pull-down FET is more than twice as "strong" as the pull-up. At 5v the "typical" pull-up current limits at about 20 mA into a LED or 25 mA into a short-circuit (so is probably "safe"). The corresponding pull-down current limits at about 50 mA and 60 mA respectively (from the supply rail). The "Absolute Maximum" rating (from the start of section 30 in the corresponding M2 data sheet) specifies 25 mA for the output FETs and 20 mA for the output "clamp" (electrostatic protection) diodes.

But at 3 volts, the limiting FET currents are much reduced and the PICaxe probably won't "self destruct" even into a short circuit (there are of course still plenty of ways to physically destroy it ;) ). And at 1.8 volts the maximum output currents are absolutely pathetic at 1.5 - 8 mA (depending on chip temperature, etc.).

As hippy implied, the failure mode is probably over-dissipation (overheating) in a very small area of the chip, which I would expect to create a short-circuit (or low impedance) to ground. The bond wires (which would blow open-circuit, like a fuse) are probably all the same diameter and rated for at least the supply rail / ground pin limits of around 80 mA (although using multiple bond wires for those is a slight possibility).

Cheers, Alan
 
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