Hey Linden,
For reference this is the product page link.
DC-DC Adjustable Step-down Module 5A 75W
CC = Constant current or current limit.
CV = Constant voltage or voltage regulation
As Bob mentioned before, to adjust the output limits with the potentiometers keep in mind “the adjustment knobs are 30-turn potentiometers that control the voltage and current limits. This means you may have to turn them up to 30 turns to get from the top of the output limit range (36V) to your target voltage.”
Hope this summary helps!
Can this be used to regulate power down from 5Vdc to 3.7Vdc?
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Hi Ravneet,
The headroom voltage of this regulator is 3V, so to get an output of 3.7V you would need 6.7V,
We might be able to help more if you tell us what are you trying to achieve?
Thank you for getting back to me!
I’ve got an existing LED system that uses a li-ion 5400mAh 3.7v internal battery, and I’m looking at remove that existing battery and upgrading it to be able to use swappable 6000mAh 3.7v batteries that are individually chargeable. The idea is to extend the operating time for the existing LED system. These swappable batteries would act as power banks essentially.
The existing board that runs the LEDs has +/- pads where the existing 3.7v battery is solders into.
The issue is that most charging boards_
for 3.7v li-ion batteries that I’ve looked at charge on your website offer around 200mA-500mA charging current which would take ages to charge a 6000 mAh battery. There is one board that I’ve found, however, that might be able to charge the battery at 2000 mA, but the only downside with that board it has a 5V boost circuit that outputs 5V 2A via a USB-A connector.
I’m uncertain if existing hardware on the LED’s board can accept 5V power, I can’t identify the parts to be able to look at the datasheet to check this. To play it safe, I’d like to be able to supply it with 3.7V.
I’ve flirted with the idea of using a PD power bank instead with a buck converter.
I’d definitely appreciate some suggestions!
Below are some links to the hardware that I’ve looked at on your website:
https://core-electronics.com.au/lipo-rider-plus-chargerbooster-5v24a-usb-type-c.html?gad_source=1&gclid=Cj0KCQiAqL28BhCrARIsACYJvkcLuEcZMngnPexel2jb7o-mABWvrGHv3aKlmelJV5m1pYQ2Mp-VKl8aAu9JEALw_wcB
https://core-electronics.com.au/polymer-lithium-ion-battery-6000mah.html
https://core-electronics.com.au/lipo-amigo-lipoliion-battery-charger-lipo-amigo-pro.html (just ordered this to try out)
Cheers,
Rav
What does the blue led on the step down module mean
Hi Rav,
I was looking into doing something similar. I’m trying to power a transmitter device that takes 3.7V supply from the 5V rail of my Raspberry Pi Zero 2 W. I found this was successful as a step down converter and was able to adjust the trimpot to the appropriate voltage.
After almost a month however I found that the output voltage was stuck at a range of 4.3V-5V and was wondering if anyone had experienced something similar. I did try turning the trimpot in each direction to its maximum but no change.
Any advice would be appreciated.
Hi all,
I was doing some basic tests with this unit a few months ago - following the steps on how to set voltage and amps as per this video: https://www.youtube.com/watch?v=rDkP97-BHXI&t=334s&ab_channel=CoreElectronics
I am powering with a supply rated at 24v, 1A. Turning the first potentiometer allows me to adjust the output voltage to the desired 18v. Turning the second potentiometer doesn’t appear to do anything - but the output starts from 100ma and then appears to climb to 500ma.
Pretty sure I had this working as intended without issue when I first used it, getting the desired 700ma output without incident. Any ideas what might be going on? Have I borked the unit in some way, or is my MM broken (checked the fuse - seems fine).
Also if someone can explain how we measure amps from the output of the device while there’s no load on the end (again, as per the video) that might help me understand a little more also.
Hi James
The second potentiometer is a current LIMIT control. Usually set with a short circuit on the output or a low value resistor.This becomes the MAXIMUM current the device will deliver (if it is working properly). If the load requires less current than this then that is what it supplies but if the load somehow requires more (ie; the resistance lowers) the device will only supply the current it is set for. If this happens it is quite normal to see a lower voltage as this is normally the method used to maintain the set current.
If you are measuring current with a DMM the meter itself is the load. The meter will have some resistance depending on the range. If the 10A (or 20A depending on meter) this will be quite low but if on the mA ranges can be pretty high and there will be a voltage drop across the meter itself. This is called the “Voltage Burden” and expressed in V per mA and can be high enough to affect the operation of any device under test (DUT) so it is not very accurate or indeed advisable to use a DMM on the mA ranges to measure current in low voltage circuits in this manner.
Cheers Bob
Hi Bob, thanks for your answers.
Ok I undersand your first point - the second pot is the limit, not necessarily the ‘output’ per se (although depending on the load these values can appear to be the same). So unless I have something that draws at least 700ma, I’m not going to be able to measure 700ma with my MM. Is that fair enough to say? What sort of draw would you expect a DMM to have when running in 10A? The engineer in this video https://youtu.be/rDkP97-BHXI?t=326 seems to be able to draw 750ma - 1.3A so I have to assume his MM pulls at least that much.
If this is the case I should be able to set the limit as he does. However as I mentioned turning the pot doesn’t seem to change the amperage - this goes up by itself. I disconnected the unit when I thought I smelled something. Could a short-circuit cause the behaviour I’ve described? The unit is pretty much new and hasn’t seen a lot of use, which is why I’m puzzled.
Hi James
To set the current limit connect the DMM (10A range for higher currents) straight across the device output with the limiter pot at minimum, probably fully CCW. Be aware this is a multi turn pot (10 or 20 turns) and a slight “clicking” sound will be heard when the limit is reached. This is normal and you are not causing any damage. The output voltage will probably read close to zerozero at this point. The required voltage should be set first with the output open circuit.
Now advance the current limit until the required maximum current is reached.
You are now ready to go.
Tip. If your load requires say 700mA do not set the limit to this figure or you will have possible limit/voltage sag problems. Set the limit a bit higher say about 800mA to 1A.
Cheers Bob
If this does not work you are doing or have something wrong.
Hi Bob,
Thanks once again for your reply. Shifted to a different supply to test - 5v 4a. I don’t seem to get any sensible readings from the MM when I follow the steps above - I get what seem to be floating, rising values. I’ve also tried putting the meter in series in another simple circuit and again seem to just see rising values. Starting to wonder if my problem is with the meter.
Oh and during this more recent test the wires running from the meter to the props get quite warm. Is that to be expected or do I indeed have a short somewhere?
Hi James
You don’t by any chance have the meter set for AC volts do you. That would give some funny looking results.
This would indicate a higher current, in the order of a few amps. This is normal for this sort of current but would not be expected if the current only in the mA range. Most DMM handbooks of any repute will give you a maximum time for measuring 10A or so due to the heat build up in the test leads. I assume you are using the leads that came with the meter and not just some bits of wire you happen to have.
Can we have some sort of diagram of your measurement set up please. If the meter is indeed set to measure DC amps you are doing something wrong or the meter itself is indeed faulty.
Cheers Bob
Hi Bob,
Seems like I had multiple failures. Confirmed that the MM was not measuring amps correctly - fuse was ok but the shunt looked like it had a fracture. Replaced the unit and started getting readings that made a little more sense.
Measuring the step-down module with the non-faulty MM I don’t see floating amp readings, but I still can’t get the output amperage I want - turning the pot doesn’t seem to get me anything above 20ma. I’ve since received a new step-down module and this is behaving exactly how I remember, and exactly how the video illustrates. I can only assume that through testing this module I’ve somehow broken it, which is disappointing - I really haven’t done anything extraordinary to it. I expected it would have stood up to a little more punishment.
Hi James
Yes multiple faults can be a problem. Especially when one is your measuring instrument
Thanks for letting us know the outcome.
Cheers Bob
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I cant seem to find the datasheet for this. Are the input and output grounds common, or are they isolated?
Hi James
Like most of this sort of thing detailed information is very iffy or completely non existent.
Check with your DMM. Measure the resistance between the 2 ground connections. I think they are common but best make sure.
Cheers Bob
Ok ground plane looks the same since there’s little to no resistance. So my take is that it’s not isolated.
Also for what it’s worth - has anyone found these to be incredibly brittle? Seems like I’ve managed to break three of them incredibly easily (trim pots no longer change voltage / ampage). Frustrating.
Hi all - I just accidentally found another supplier of this product who remarks that “The module uses a low-side current measurement, so the ground of the input and output are not the same.”. If correct, this is important - the module cannot be used as a 3-terminal regulator (at least, not with current limiting).
For beginners, it means that the current must return from the load into the -ve output terminal, and then from the -ve input terminal back to the power supply. In other words, the supply must be connected only to the input terminals, and load only to the output terminals. The -ve of the supply and the -ve of the load cannot be otherwise connected - they cannot both be earthed for example. If they are, the regulator will produce the set output voltage, but the current limit pot won’t do anything because the current measuring part of the circuit has been bypassed.
Hope this helps. It might explain why several users have trouble with the current limiting. Perhaps someone could verify that the two -ve terminals are not directly connected (there may be only a very low resistor in the path)?
Hi Roger
Good find. A bit of VERY important info not available at other vendor sites.
Quote
“Note: The module uses a low-side current measurement, so the ground of the input and output are not the same.”
End quote
One reason I personally would not purchase. Not enough info available. I can never understand the keeping of these “secrets” If manufacturers are worried about people copying and making their own modules at the price of the made up device who would bother. But I for one do like to evaluate fit for purpose before I outlay $$$ and with a lot of different devices this info is sadly lacking. So I seek another path.
Cheers Bob
Hi James
A bit late replying BUT
Just how do you manage to “break” these pots. When they get to the end they just ratchet over this point and do nothing. You can hear a “clicking” noise at this point. It makes a noise but no damage is being done.
They will always appear to stop working when you get to the maximum voltage which will be about 3 Volts or so below the input voltage.
As for your current. The source supply has to provide this so even though the spec says 5A you won’t get this if your source won’t supply it.
So there are several reasons why the pots don’t seem to work as you expect. All explainable.
Cheers Bob
