Does anyone know of something I can buy that uses batteries and outputs a stable 5v DC (irrespective batter voltage being say 9v) ?

I just want something I can put batteries in and has 2 output pins 5v and Gnd - I want to use this to supply power to an STM32 board.

Searched Amazon but nothing jumped out at me!

Thx

 

You make no mention of a power requirement but you may want to start with a Google of "DC to DC Converters". You want one with 5.0 Volts out and a wide input range or a range fitting whatever you want. Here are a few examples but there are hundreds to choose from out there.

Ron

 

Why don't you use a 5V 1A wallwart? All you need is the mating barrel jack. Solder 2 leads on poke those into your breadboard rail.

 

I just posted an article "A Computer Based Master for ITR & IBM Minute Impulse Secondary Clock Movements”, a few minutes ago and I have two schematics and a write up in the appendix in this article discussing a battery backup system. I also posted a schematic a few months a go about the same circuit, using a DC to DC buck converter with an adjustable output , 3 amps out max and input voltages up to 30 volts. The article uses it for battery backup for the Rasberry Pi Zero W . Joe

 

Hi, yes I made no mention of power requirements because I would eventually select some specific model from whatever range of products.

This is a requirement to have the board and any peripherals totally decoupled from an electricity supply outlet, batteries must be used.

I can easily put something together with (for example) stuff like this and this but wondered if there were encapsulated battery packs that had all this in them.

 

Have you thought of using one of these... https://www.amazon.com/s?k=power+pa...refix=power+pack,aps,1235&ref=nb_sb_ss_i_3_10

 

Have you thought of using one of these... https://www.amazon.com/s?k=power+packs+for+cell+phones&crid=3MVIQYR8CV5ES&sprefix=power+pack,aps,1235&ref=nb_sb_ss_i_3_10

Caution with running development boards with Power Banks

One thing I found when trying to power a microcontroller development board, Power Banks require a minimum load. Without enough load, they shut off after about 10 to 20 seconds. The minimum load on my Power Bank was about 100 mA. This is to prevent interface circuitry on a load which is always on, even though the load device is "off", from draining the battery over time. Cypress Semiconductor and others make Power Bank control chips and this behavior is documented for the ICs but not documented for Power Banks. Not a problem for most uses but, of course, it took up a few hours of my time figuring it out. What was confusing was the dev board would boot and run but then die like something was wrong with the microcontroller. My solution was to increase the power bank load with a resistor in parallel with the development board power input. With the minimum load requirements met, the Power Bank worked great and my little robot was free to go.

 

Hi, yes I made no mention of power requirements because I would eventually select some specific model from whatever range of products.

This is a requirement to have the board and any peripherals totally decoupled from an electricity supply outlet, batteries must be used.

I can easily put something together with (for example) stuff like this and this but wondered if there were encapsulated battery packs that had all this in them.

Then rather than DC to DC converter as shown in the link I provided a Google of "USB Battery Pack" will bring up plenty of options. Here are a few from Amazon. So you can roll your own using a DC to DC converter or run with an existing off the shelf solution, again depending on your needs and or wants.

Ron

 

Then rather than DC to DC converter as shown in the link I provided a Google of "USB Battery Pack" will bring up plenty of options. Here are a few from Amazon. So you can roll your own using a DC to DC converter or run with an existing off the shelf solution, again depending on your needs and or wants.

Ron

Yes I saw those USB portable chargers, I take it people here have good experiences with these?

Thanks

 

Yes I saw those USB portable chargers, I take it people here have good experiences with these?

Thanks

Did you see my post #7? Mine was an NXP KL25 board but just like an STM32. Works great and plugs into the USB debug port, if your board has one. Easy but see the post about minimum load.

 

Did you see my post #7? Mine was an NXP KL25 board but just like an STM32. Works great and plugs into the USB debug port, if your board has one. Easy but see the post about minimum load.

Thanks, and yes I read (just now!) that post and what you said about the auto shut off. Frankly I do not like that one bit, so I'm glad you mentioned it.

Battery life is pretty important and intentionally draining it isn't ideal (for me anyway). I can perhaps just stick with some raw batteries and add a simple regulator, be better if one could elect to have the shut off or not but I guess not.

100 mA is a large current and an idle system if fully charged would be dead in about a 10 days or so.

This post confirms what you say, I guess this is all due to the fact that these devices are intended to rapidly charge some other device not act as long term batteries in and of themselves.

Seems that these are the type of batter technology inside these chargers, I assume the raw batteries do not have this auto shut off feature.

 

Hmm these "LiPo" batteries seem very good, I'm actually toying with the idea of making a small autonomous "robot" (I did this back in the late 70s with an 8 bit 6502) just for the heck of it and these batteries seem good.

Two cells yields around 7.5 V and the simple DC regulator I was looking will generate stable 5V from an input of 6V or more.

 

A USB power charger already puts out 5VDC regulated.

 

A USB power charger already puts out 5VDC regulated.

If you mean the kinds of devices discussed above then yes but they have that annoying "auto shut off" feature if current draw drops below 100 mA.

 

You might check out Adafruit.com; they carry a variety of LiPo-based power solutions. This item combines a charger controller circuit for a 3.7V LiPo cell with a step-up DC-to-DC converter that takes power from the LiPo to generate a 5 VDC output at up to 1 amp.

 

You might check out Adafruit.com; they carry a variety of LiPo-based power solutions. This item combines a charger controller circuit for a 3.7V LiPo cell with a step-up DC-to-DC converter that takes power from the LiPo to generate a 5 VDC output at up to 1 amp.

You're right, that is a nice solution in that it steps up the 3.7v to 5v, I like this a lot.

 

Define your requirements first. If you only need 1mA and you end up with a 1A supply, it's going to waste a lot of power. If you don't care about a little ripple and some EMR then a DC/DC buck/boost will be very efficient, but if noise is critical then linear, or a combination switcher and linear solution may be best. If EMR is an issue then you may have to go all linear components, or at least be very careful in your buck/boost selection. There are a ton of options, each with its own advantages and disadvantages.

 

? https://www.google.com/search?tbm=isch&sa=1&q=quiet+step+down+DC/DC+converter+regulated+5V+2A+650kHz
(includes) http://cn.21ic.com/ebook_download/microsite/Linear/PbLJournal-V1N1-2018-01.pdf (Figure 3. Gizmo layout Pg.28 - specifies what it says)

 

Regardless of which way you go with this when considering a battery solution in a roll your own make sure you also consider the battery charging solution.

Ron

 

Caution with running development boards with Power Banks

One thing I found when trying to power a microcontroller development board, Power Banks require a minimum load. Without enough load, they shut off after about 10 to 20 seconds. The minimum load on my Power Bank was about 100 mA. This is to prevent interface circuitry on a load which is always on, even though the load device is "off", from draining the battery over time. Cypress Semiconductor and others make Power Bank control chips and this behavior is documented for the ICs but not documented for Power Banks. Not a problem for most uses but, of course, it took up a few hours of my time figuring it out. What was confusing was the dev board would boot and run but then die like something was wrong with the microcontroller. My solution was to increase the power bank load with a resistor in parallel with the development board power input. With the minimum load requirements met, the Power Bank worked great and my little robot was free to go.

No place did I see any mention of how tight the regulation needs to be, or a specific current, or the hoped for efficiency.
You could use a six volt gell cell and a series low drop out linear regulator IC and it would work and last a fair amount of time, probably. But it would not be especially efficient.