Forgot to answer the other part of your question: using a Bluetooth board as a test load is probably fine. It may have spiky, inconsistent current draw which makes it hard to get solid readings from, but it will definitely prevent the short circuit scenario.

Note that you still need different wiring configurations for current vs. voltage measurements. I'd suggest you read all three links in my previous post, just to make sure it really makes sense, before proceeding.

Thank you so much, I study this and try to make everything work, I will let you know if everything works nice or if there is a problem!

 

Hi everybody, it's me again,

I have been busy on another project so I could not test what I wanted until now,
I made this setup (see attached picture)

First I wanted to use a diode to protect the circuit but it seems like the diode is too strong and the Bluetooth chip doesn't work if I use it, so I tried without a diode and the Bluetooth chip seems to work, the thing is that I still have this voltage drop problem on my batteries, when I unplug everything and use the multimeter to measure the voltage it is very low, like 2.5V and then after few minutes it becomes high again.
It is a big problem because I want to plug the Bluetooth chip after the voltage regulator so it works with the good voltage but I also want to plug a stepper motor that requires a higher voltage before the voltage regulator, and it looks like it is impossible because the voltage of my batteries drop very fast if I use the voltage regulator.
I Don't know if the problem comes from the voltage regulator or maybe one or both of the batteries are dead.
To be sure that the voltage regulator wasn't dead I used a new one.
Thanks in advance for your help.

 

Hi everybody, it's me again,

I have been busy on another project so I could not test what I wanted until now,
I made this setup (see attached picture)

First I wanted to use a diode to protect the circuit but it seems like the diode is too strong and the Bluetooth chip doesn't work if I use it, so I tried without a diode and the Bluetooth chip seems to work, the thing is that I still have this voltage drop problem on my batteries, when I unplug everything and use the multimeter to measure the voltage it is very low, like 2.5V and then after few minutes it becomes high again.
It is a big problem because I want to plug the Bluetooth chip after the voltage regulator so it works with the good voltage but I also want to plug a stepper motor that requires a higher voltage before the voltage regulator, and it looks like it is impossible because the voltage of my batteries drop very fast if I use the voltage regulator.
I Don't know if the problem comes from the voltage regulator or maybe one or both of the batteries are dead.
To be sure that the voltage regulator wasn't dead I used a new one.
Thanks in advance for your help.

It's hard to see clearly in the picture - at the regulator, are both black wires connected to pin 2 (the middle pin?) If so, the wiring looks ok to me.

Have you tried measuring the voltage at the regulator output/bluetooth module input? If it's significantly over 3.3V, that would be a sign that the regulator was malfunctioning.

Do you have specs on the Bluetooth module? Do you know how much current it should be drawing?

It's entirely possible that you do have bad batteries and/or regulators, but it's never my first assumption to blame the parts.

 

It's hard to see clearly in the picture - at the regulator, are both black wires connected to pin 2 (the middle pin?) If so, the wiring looks ok to me.

Have you tried measuring the voltage at the regulator output/bluetooth module input? If it's significantly over 3.3V, that would be a sign that the regulator was malfunctioning.

Do you have specs on the Bluetooth module? Do you know how much current it should be drawing?

It's entirely possible that you do have bad batteries and/or regulators, but it's never my first assumption to blame the parts.

Hello,
Yes the black wire are both connected to pin2,
I first measured the current on the regulator output/Bluetooth module input, it was first 3.7V, then I asked a colleague to take a picture while I was measuring the current and the voltage had drop sifgnificantly, he took 2 picture at a few second of interval and you can see on them that the voltage keeps dropping (attached file).
The bluetooth module is a nrf51822, the maximum voltage supported is 3.6V, this is why I am using this LDO.

I am sure that the voltage regulator is not dead because it is the third one I use to be sure. Maybe one battery is dead, but would it be the result if it was? because I measure the current drawned by the batteries just before I used them and they were both 4.2V.

I checked the two batteries individually, one is 4.07V, the other one dropped until 1.35V, so my idea is that a battery is dead Don't you think?

Thanks again for your help.

 

Hello,
Yes the black wire are both connected to pin2,
I first measured the current on the regulator output/Bluetooth module input, it was first 3.7V, then I asked a colleague to take a picture while I was measuring the current and the voltage had drop sifgnificantly, he took 2 picture at a few second of interval and you can see on them that the voltage keeps dropping (attached file).
The bluetooth module is a nrf51822, the maximum voltage supported is 3.6V, this is why I am using this LDO.

I am sure that the voltage regulator is not dead because it is the third one I use to be sure. Maybe one battery is dead, but would it be the result if it was? because I measure the current drawned by the batteries just before I used them and they were both 4.2V.

I checked the two batteries individually, one is 4.07V, the other one dropped until 1.35V, so my idea is that a battery is dead Don't you think?

Thanks again for your help.

Seems odd to me that the regulator output would be 3.7V at first, when it's supposed to be a 3.3V regulator. If it's really putting out 3.7V sometimes, something's wrong.

You said you were measuring current several times in your last post, but then you retorted voltages. Were you measuring voltage or current? Those are two very different things. If you tell us the wrong thing, it makes it much harder to diagnose your problems.

I can't believe I didn't notice this or ask before, but I don't see any capacitors on your breadboard. The datasheet (page 8) recommends a 0.33uF, or larger, capacitor from input to ground. Most linear regulators also work better with a cap on the output as well, although I don't see that discussed in your datasheet.

Finally, the voltage readings on your individual batteries certainly make it sound like one of them is bad. If you've got an LDO and only need 3.3V output, do you even need two batteries in series? What happens if you set the bad battery aside and run the good battery through your LDO to power your Bluetooth module?

 

Seems odd to me that the regulator output would be 3.7V at first, when it's supposed to be a 3.3V regulator. If it's really putting out 3.7V sometimes, something's wrong.

You said you were measuring current several times in your last post, but then you retorted voltages. Were you measuring voltage or current? Those are two very different things. If you tell us the wrong thing, it makes it much harder to diagnose your problems.

I can't believe I didn't notice this or ask before, but I don't see any capacitors on your breadboard. The datasheet (page 8) recommends a 0.33uF, or larger, capacitor from input to ground. Most linear regulators also work better with a cap on the output as well, although I don't see that discussed in your datasheet.

Finally, the voltage readings on your individual batteries certainly make it sound like one of them is bad. If you've got an LDO and only need 3.3V output, do you even need two batteries in series? What happens if you set the bad battery aside and run the good battery through your LDO to power your Bluetooth module?

I'm sorry, I'm using the wrond word, I speak about voltage of course, but yes I had measured a 3.7V in the input of the Bluetooth module, I Don't use capacitors because at the moment I Don't have some, I ordered them but still waiting for them to arrive, anyway I saw in some ressources that it is only use to reduce the noise so I was thinking that it has Nothing to do with the voltage, tell me if I am wrong, I am still Learning all this things so probably I say some stupid things often.

When I use only one battery the voltage keeps changing between 3 and 3.5V, but this is probably due to the fact I am not using capacitors as you told me.
I need two batteries because I need to use a stepper motor also hat requires a higher voltage, for this one I have no problem with the voltage because it's driver take care of it.
I am using the LDO to power the Bluetooth chip and the driver will be directly connected to the batteries.

 

I'm sorry, I'm using the wrond word, I speak about voltage of course, but yes I had measured a 3.7V in the input of the Bluetooth module, I Don't use capacitors because at the moment I Don't have some, I ordered them but still waiting for them to arrive, anyway I saw in some ressources that it is only use to reduce the noise so I was thinking that it has Nothing to do with the voltage, tell me if I am wrong, I am still Learning all this things so probably I say some stupid things often.

When I use only one battery the voltage keeps changing between 3 and 3.5V, but this is probably due to the fact I am not using capacitors as you told me.
I need two batteries because I need to use a stepper motor also hat requires a higher voltage, for this one I have no problem with the voltage because it's driver take care of it.
I am using the LDO to power the Bluetooth chip and the driver will be directly connected to the batteries.

We're making progress. Keep up the good work!

Although there are some situations where capacitors are used as noise filters, which may be optional if you're sure there's no noise, I don't think this is one of them.

Many regulators will oscillate if they don't have the right capacitor(s) on their input and/or output. I don't know if that's what's causing your weird output voltages, but it seems plausible. I would get some capacitors on the regulator input and output before doing more testing. You could use the 0.33uF listed as minimum in the datasheet, or maybe go a little higher. A pretty typical value in my limited experience is anywhere from 0.1uF-10uF for both the input and the output. Even better is to have a pair of caps in parallel with each other, one large and one small, but that's probably overkill for now. I'd probably start with 1uF on each side and see how things go.

Let's focus on getting a good, stable 3.3V out of your regulator before worrying about multiple batteries again. I'm guessing you do have one bad battery and one good one, but it's hard to be sure of anything until we start getting some stable voltage readings that make sense!

 

We're making progress. Keep up the good work!

Although there are some situations where capacitors are used as noise filters, which may be optional if you're sure there's no noise, I don't think this is one of them.

Many regulators will oscillate if they don't have the right capacitor(s) on their input and/or output. I don't know if that's what's causing your weird output voltages, but it seems plausible. I would get some capacitors on the regulator input and output before doing more testing. You could use the 0.33uF listed as minimum in the datasheet, or maybe go a little higher. A pretty typical value in my limited experience is anywhere from 0.1uF-10uF for both the input and the output. Even better is to have a pair of caps in parallel with each other, one large and one small, but that's probably overkill for now. I'd probably start with 1uF on each side and see how things go.

Let's focus on getting a good, stable 3.3V out of your regulator before worrying about multiple batteries again. I'm guessing you do have one bad battery and one good one, but it's hard to be sure of anything until we start getting some stable voltage readings that make sense!

I've seen your reply a few late, I already ordred some capacitors, 0.33uF, as said in the documentation, I ordered 10 of them (0.05€ unit) so I will hase some stock, I also ordered a new battery, It's cheap so no problem and I will be sure it works , I will test this when I receive it and tell you how it is going on!

 

I've seen your reply a few late, I already ordred some capacitors, 0.33uF, as said in the documentation, I ordered 10 of them (0.05€ unit) so I will hase some stock, I also ordered a new battery, It's cheap so no problem and I will be sure it works , I will test this when I receive it and tell you how it is going on!

Good luck with the new parts! As I said before, although the datasheet doesn't require a cap on the output, it may be helpful. I'd put one each on input and output just to be sure. Between that and your new battery, I bet you'll be up and running. Cheers!

 

Good luck with the new parts! As I said before, although the datasheet doesn't require a cap on the output, it may be helpful. I'd put one each on input and output just to be sure. Between that and your new battery, I bet you'll be up and running. Cheers!

I think it works!!!!!
I received all what I ordered, and I made the Following setup Following your advice (see attachment)
And it seems to work, I still have a voltage that is a few too high in my opinion because the LDO should provide a stable 3.3V and the measured voltage is more like 3.38V-3.4V, I Don't know if it is a problem, anyway the Bluetooth chip can support up to 3.6V so it works, the only thingis that I'm scared that it reduce the lifetime of the LDO.
I used capacitors in input and output as you adviced me, and it provide a more stable voltage so I guess I should keep this configuration.
Let me know what you think about this higher voltage thant expected.
Thank you so much again!!

 

I think it works!!!!!
I received all what I ordered, and I made the Following setup Following your advice (see attachment)
And it seems to work, I still have a voltage that is a few too high in my opinion because the LDO should provide a stable 3.3V and the measured voltage is more like 3.38V-3.4V, I Don't know if it is a problem, anyway the Bluetooth chip can support up to 3.6V so it works, the only thingis that I'm scared that it reduce the lifetime of the LDO.
I used capacitors in input and output as you adviced me, and it provide a more stable voltage so I guess I should keep this configuration.
Let me know what you think about this higher voltage thant expected.
Thank you so much again!!

You're very welcome. Congrats. You're making good progress here.

Well, the regulator claims +/-2% accuracy, which would only allow up to 3.366 max, so at first glance it would appear that your regulator is a little bit out of spec. However, multimeters have accuracy tolerances as well, and unless you have a very nice, expensive meter, your meter accuracy could be looser than the regulator's 2% specs... all of which is a long winded way of saying I wouldn't worry about that voltage reading at all, unless something else misbehaves and gives you reason to be suspicious. I think you're probably in good shape there.

There is one thing I didn't think to mention or warn you about, which you should double check. It looks like you're using aluminum electrolytic capacitors, which are one of the several types of caps which are polarized, meaning they have a positive and a negative pin, and the orientation matters (many other caps are non-polarized and so their orientation doesn't matter, just like resistors.)

Unfortunately, I can't clearly see the markings on your caps, so I can't check based on that picture, but if you haven't already done so, you should make sure your caps are oriented properly. Both caps should have their negative pin connected to the middle regulator pin (ground.) Capacitor markings aren't as standardized as we'd like, but here are a couple pics that show most of the marking schemes. Looks to me like yours will match the top pic, second from the right. If the polarity is reversed, catastrophic failure can result, so you'd need to fix it ASAP. If they're already correct, then I think you're in good shape. Have fun!

 

You're very welcome. Congrats. You're making good progress here.

Well, the regulator claims +/-2% accuracy, which would only allow up to 3.366 max, so at first glance it would appear that your regulator is a little bit out of spec. However, multimeters have accuracy tolerances as well, and unless you have a very nice, expensive meter, your meter accuracy could be looser than the regulator's 2% specs... all of which is a long winded way of saying I wouldn't worry about that voltage reading at all, unless something else misbehaves and gives you reason to be suspicious. I think you're probably in good shape there.

There is one thing I didn't think to mention or warn you about, which you should double check. It looks like you're using aluminum electrolytic capacitors, which are one of the several types of caps which are polarized, meaning they have a positive and a negative pin, and the orientation matters (many other caps are non-polarized and so their orientation doesn't matter, just like resistors.)

Unfortunately, I can't clearly see the markings on your caps, so I can't check based on that picture, but if you haven't already done so, you should make sure your caps are oriented properly. Both caps should have their negative pin connected to the middle regulator pin (ground.) Capacitor markings aren't as standardized as we'd like, but here are a couple pics that show most of the marking schemes. Looks to me like yours will match the top pic, second from the right. If the polarity is reversed, catastrophic failure can result, so you'd need to fix it ASAP. If they're already correct, then I think you're in good shape. Have fun!

View attachment 165788
View attachment 165789

Thank you very much, I checked this and it was ok, I made a lot of progress by your help, I think I am on the right way now, maybe you will see an other post from me if I have some other problems^^
Best regards!​

 

You're very welcome. Congrats. You're making good progress here.

Well, the regulator claims +/-2% accuracy, which would only allow up to 3.366 max, so at first glance it would appear that your regulator is a little bit out of spec. However, multimeters have accuracy tolerances as well, and unless you have a very nice, expensive meter, your meter accuracy could be looser than the regulator's 2% specs... all of which is a long winded way of saying I wouldn't worry about that voltage reading at all, unless something else misbehaves and gives you reason to be suspicious. I think you're probably in good shape there.

There is one thing I didn't think to mention or warn you about, which you should double check. It looks like you're using aluminum electrolytic capacitors, which are one of the several types of caps which are polarized, meaning they have a positive and a negative pin, and the orientation matters (many other caps are non-polarized and so their orientation doesn't matter, just like resistors.)

Unfortunately, I can't clearly see the markings on your caps, so I can't check based on that picture, but if you haven't already done so, you should make sure your caps are oriented properly. Both caps should have their negative pin connected to the middle regulator pin (ground.) Capacitor markings aren't as standardized as we'd like, but here are a couple pics that show most of the marking schemes. Looks to me like yours will match the top pic, second from the right. If the polarity is reversed, catastrophic failure can result, so you'd need to fix it ASAP. If they're already correct, then I think you're in good shape. Have fun!

View attachment 165788
View attachment 165789

Hello! It's me again!
Happy new year to you!
I have a new problem, still with my LDO, it appears that I give it too much power, when I use the 2 batteries in series, and I plug my Bluetooth chip to the circuit (with the LDO of course), my Bluetooth chip is visible but I can't connect to it, I can if I use only one battery, someone on another forum told me that it is because the LDO has a thermal shutdown that reset my Bluetooth chip continuously, but the LDO support up to 24V in input, maybe I give it too much current, I Don't know, I am looking to reduce the input to the entry of the LDO but I Don't know how I could do that.
I am completely lost, if you have any idea it is very welcome!
Thank you!

 

I apologize - I'm pretty short on time right, so I haven't re-read the whole thread to check things. If any questions here are redundant, I'm sorry.

How much current is the Bluetooth module drawing?

Is the voltage of the regulator output roughly the same in both configurations (1 vs 2 batteries?)

Does the metal case of the regulator feel hot? If so, are we talking about so hot that you jump back, just hot enough to be pleasant on a cold winter day, or somewhere in between?

The 24V input rating on your LDO isn't as meaningful as it might seem. It does mean you shouldn't supply more than 24V, but it does not mean than anything under 24V is ok. The real limiting factor in most scenarios is heat.

Off the top of my head, I wouldn't have expected you to have heat problems. If you're dropping around 5V across regulator, you could deliver 200mA at 1W heat dissipation, which I'd expect to be ok without a heat sink. If you only draw 100mA, that would be 1/2W dissipation, which should really be ok. But you can't trust my memory. You need the actual current draw of your circuit, and the thermal limits from the regulator datasheet.