Elego breadboard power supply only providing 4.96V

@yurkshirelad I'll get on it. It shouldn't take but a couple days at most. You could do just the 5v and 3.3v regulators, but you'll have more heat in the 5v regulator as it burns off the excess voltage.  If you can find something that will provide 7vdc input, it will give you the regulated 5.  I knew I'd be working with motors eventually, so went up to 12 volt.

Anyway, it's really late, so I'll get on when I get up.

Couldn't sleep......  looks like it only took 3 hours.  🙂

I'll look up the part numbers for the fuse holder clips if you'd like. I used a random switch and LED, otherwise I have datasheets for all. (except for the headers, got plenty from an e-bay listing a couple years ago. so no part number or data sheet.)

I'll pop in tomorrow sometime for questions or comments.  As for now, I think I'll go play dead for a few hours. (hopefully)

@yurkshirelad My observation is no jumper means no voltage

@dronebot-workshop I ran the test with a small load (fan) and in the end from the 4 power supplies I have:

• 1 DOA - worked once, then would not power on
• 1 faulty left power rail (passes through 9v), although other side seems good (I have little confidence)
• 2 with "acceptable" voltages  4.96/3.344 and 4.97/3.256

A bit of Googling reveals not too many options. Either the cheap breadboard power supplies, DIY with buck converters etc., or a a benchtop power supply (DIY ATX conversion or purchased). We have nice instructions right here in the Workshop for the DIY options! 

Posted by: @theoutlander

We have nice instructions right here in the Workshop for the DIY options! 

And here they are:

You'll find in most cases the buck converters are a better option, as they are more efficient. However, there are a few low-drop linear regulators that are much more efficient than the old 7805 devices.

😎

Bill

I ordered a few parts to build a simple linear voltage regulator, my first circuit. Actually 2 linear voltage regulators; 3.3V and 5V. Then I'll work out how to merge them or make them selectable and other fun stuff like that. Hopefully my wife won't see what I tacked on to the purchase! Luckily it wasn't an oscilloscope or anything like that! 🤣

@dronebot-workshop

I guess, the breadboard power supply module has a voltage drop of 0.04V. Thus, it provides us 4.96V of terminal voltage. Otherwise, the multimeter is a bit inaccurate. 

It happens with almost all voltage regulators. Even the 5V supplied by the Arduino is actually 4.96V. 😉 

@sumanta

Not really accurate in that most of the time, notice I said most, it's is the inaccuracy of the meter measuring the voltage.  But then again most devices work in a range either slightly below or slightly above the stated requirement.  It is just so much easier to us even numbers to give voltages requirements.  Although the 3.3V devices throw that statement out the window doesn't it?

Take for example the battery voltage of a car.  Mostly they are labeled as 12V, but they are rarely that exact voltage.  Or the voltage of your mains.  Here in the states it is usually referred to as 110V AC at 60Hz, but if I was to measure mine right now, I'd more than likely get a reading of 125V and since things are usually pretty stable on our power grid the frequency might be spot on at 60Hz.  Unless you live in Texas here in the states right now! 🤣 😎 

@codecage

Yes. You are right. You see, the devices can't be that accurate most of the time. 😉

But a slight inaccuracy won't lead to any damage. 

I poked around the numerous cheap Chinese made bench power supplies on Amazon; how am I supposed to tell which are safe, which are good and which should be avoided? Crazy. I only really need 3.3V and 5V.

Posted by: @centari

Couldn't sleep......  looks like it only took 3 hours.  🙂

I'll look up the part numbers for the fuse holder clips if you'd like. I used a random switch and LED, otherwise I have datasheets for all. (except for the headers, got plenty from an e-bay listing a couple years ago. so no part number or data sheet.)

I'll pop in tomorrow sometime for questions or comments.  As for now, I think I'll go play dead for a few hours. (hopefully)

 

What are J2-J9?

@yurkshirelad Just female pin headers, same as you'd use on an Arduino, or esp8266, etc.  Single inline pins, 5 pins long in my case. Number of pins and type you can actually decide for yourself, I just found it convenient for dupont jumpers.  Keep it female though to prevent accidental shorts.

I tried the breadboard PS again with a new 9V wall wart I picked up, and it's providing 5V or 3.3V, not 8V or higher. I didn't read its datasheet properly and I didn't notice the text on its PCB that says "VIN 6.5V-9V"! 🙄 

Posted by: @yurkshirelad

I tried the breadboard PS again with a new 9V wall wart I picked up, and it's providing 5V or 3.3V, not 8V or higher. I didn't read its datasheet properly and I didn't notice the text on its PCB that says "VIN 6.5V-9V"! 🙄 

You made me look. The one on my bench says "12 volts". Not like I need to see magic smoke.