A couple of issues...

Products & Technology DSO Nano
#21

Ummm maybe i’m mistaken again, but i think R25 & R26 will work well for this purpose. Attaching the MOS gate to VUSB gives two posibilities:
-if USB is disconected, VUSB is low and MOS is enabled -> NANO is battery powered
-if USB is powered VUSB will be higher than 2.5V leaving a Vgs < 1.3V not enough to turn the MOS on -> NANO will be USB powered.

By the way, in the circuit depicted in the manual schematics, LTC4054 (U1) is programmed to have a programming current of 500mA. And the current required by NANO is less than that. An easy trick will be to remove D3 diode, because if NANO is USB powered, U1 will try to charge the battery but it will also supply the circuit too. Battery charge will be slower but it will be controlled by LTC4054 and not by a diode.

I’ve removed D3(S34) in my Nano and everything runs smooth…

#22

That’s just what I thought…

in my case removing the D3 diode unfortunately didn’t solve anything: done same test (charging for several hours, both in the on and off state) and the result is exactly the same as before, the battery last just about 5 minutes

so I got to the conclusion that battery or charging IC must be defective…

#23

GBian, did you charge the battery before removing D3?

If the answer is yes, you probably “destroy” the battery internal resistance, rendering it unusable. I have not charged the battery before removing D3 and i have experienced no problems so far (3 days owner).

#24

well, the battery, when I removed the diode, was rather low: not only I didn’t manage to get more tha 5 minutes of operation in any way, but if I remember well before removing D3 I had just tested again the battery life, depleting it completely (and obtaining 5 minutes of operation)…

then obviously I disconnected the battery, removed the diode, reconnected it, and connected the dso to an usb port, hoping to get a nice “battery full” icon!

unfortunately, no way… 5 minutes again

#25

P.S.

maybe I didn’t understand well, did you mean that in the non modified configuration, as shipped, with d3, charging the battery damages it?

#26

First of all i am not a battery expert, so i can’t tell you if battery was actually damaged by the diode or it is only the firmware that do not recognise the battery charge correctly. Test your battery under load and you will get an answer.

Lithium batteries are tricky to charge, and obviously a diode it is not a good charger. If you take a look at the LTC4054 datasheet, when it begins battery charge, the current is limited. With a diode such as S34 the only limitation here is provided by the USB port (which in theory its not allowed to surge more than 500mA without an external adaptor). After current limiting there is a top voltage limit arround 4.2V. That would not be the case in the diode circuit.

Disclaimer: i own a NANO and i think is a good engineered device.

#27

sorry, slimfish, I didn’t mean to attribute to you any kind of judgment on the dso… just wanted to know if I was doing it right, my only interest is to make that thing work since I also find it wonderful

anyway here are some other interesting results:

  • the battery goes down also when the dso is connected to an usb port, apparently the ltc4054 doesn’t give enough current… leaving the dso on and connected the battery does completely deplete (screen fades)

  • with the device turned off, the charger seem to manage to give some energy to the battery: after a few minutes the dso is able to turn on again, and when disconnected works correctly, even if with a low battery level

the problem is that it seems it is not able to charge fully (or half-fully) the battery, even leaving it connected for hours

#28

Ok, yes that will work. I thought you wanted to connect the gate to the junction of R25, and R26, which would not work.

You do however want to leave diode D3 installed, or your DSO will not work if the battery is dead. Also, the voltage available to the DSO with the FET circuit will be less due to the voltage drop of the forward biased diode in the FET (since it will be turned off when charging). There should be no problem leaving D3 in, if the FET circuit is added, and in fact, it would be preferable.

#29

Manton,

i agree that in a future revisión of hardware (with the FET circuit or similar) is very interesting to keep the diode as an alternative path of supply.

But with the actual revision of hardware, i think it’s better to get rid of diode (S34). It is healthy for the battery and the DSO runs without problems. Of course, if the battery is already dead removing the diode is nonsense.

#30

At last I resolved to test the charger/battery system to sort out what is going wrong, so I opened the dso and connected a couple of multimeters to the system.

I started with a depleted battery, i.e. I waited until dso turns off

the voltage on the battery, once disconnected was a few tens of mV (bad thing I suppose)

then I connected to the circuit and the LT4054 started giving 76 mA (another bad thing… shouldn’t be 500 mA, at least at start, with battery low?). immediately after chargeing started, battery voltage is 3.4 V

after about 15 minutes, battery voltage approaches 3.7 V and charge current start to decrease, with fluctuations between 0 and 76mA, that could be the way the charger works, I don’t know…

in 20 minutes charging current is 0, charging has stopped (third bad thing, the battery cannot be charged fully with 20 minutes @ 76 mA!)

last: if I turn the dso on, the charging current becomes something like -70 mA, i.e. the dso draws current from the battery. this explains why I found that with the instrument on, not only the battery didn’t charge, but it depleted instead!

these problem, I think, could originate from a defective battery that does not “take charge”, or a defective LT4054, or both… but after these tests, I do not know what else to do, so please help me getting my dso working!

thanks again

#31

If the BATTERY voltage is a few mV when disconected, you can dispose it properly, because it is actually damaged.

The 500mA limit depends also on USB current (which is also limited to 500mA). Don’t use a USB hub for DSO Nano

Get another Lithium battery and check what the charger does.

#32

first of all, thank you for the fast answer,

I was thinking about trying another battery, but I cannot find a suitable one easily. Moreover, the exact replacement (that would be the best choice to avoid doing more damage) appears to be made by Shenzhen cyclelong company, at least this is the only one I found, and anyway cannot be bought as an end-user:

szcyclelong.com/zhan.asp?id=9 model 404343, 760 mA nominal

if you could send me a replacement I would be more happy, in any case, the battery I received didn’t work correctly from start, so I think it can be replaced “under warranty” :slight_smile:

any other suggestions? I tried to test the charge without battery, but I think I’ll need a “battery simulator circuit” to get consistent results, since just putting a small resistor, doesn’t work…

#33

sorry, but I think you (slimfish) are not from seeedstudio, isn’t it?

so, obviously the “warranty replacement” request is not addressed to you!

and thanks anyway!

#34

sorry but no, i’m not from seeedstudio.

#35

Hi

I have try the charger function there days and it work well , without a charger IC and just use a diode , we also can changer the battery nearly full about 4.1V , and can use more than 2.5 hours …

so i suppose maybe your battery is bad , and maybe you charger it to long (10 hours) , the battery has a protective circuit but the DSO has not a charger circuit , so it maybe broken the battery if you charge it too long.

if you can’t found a battery to replace it , that we can sent you a new battery …sorry for our neglect that have not to remind you about the charger Attentions , it will be add to the manual next time.

#36

yes, I would be very grateful to you if you could send me a replacement battery…

Since I decided to go without diode, now there should be no problem of charge duration (the LT 4054 should take care of it).

thanks again!

#37

if you use a LT 4054 to charge , then when your battery in low power that you cannot use a USB to power the DSO , because the LT 4054 check the battery is in low power , that it will be in small current mode to charge the battery to a hinger voltage then give out constant current to charge it , when you in low power , the DSO need a large current but the LT 4054 check the battery need charge in small current mode that it will consider the battery is bad and not work ,and then you cannot use your DSO … only if your turn it off and charge the it for a moment .

and if without a battery it will not work .

#38

the battery protection circuit module was bad and prevented charging… swapped it with one from another battery and all works well. I had only an old li-polymer battery that was no more working because the cell was exhausted, so the only solution was to try exchange the circuits (risky…) and hope

well, needed a bit of work but now it’s all OK!
R0016023.JPG

#39

Hi - I received my DSO Nano yesterday and had the same problems others mention in this thread:

After charging for multiple hours, the Nano would turn on but showed minimal battery and then quickly died 1-2 minutes later. It also wouldn’t turn on and show “USB” for the batter power indicator – so it appeared that minimal charge was reaching the Nano.

In my case, I think the USB cable I also purchased from Seeedo was to blame. When I switched to a different mini USB cable (a white one from a Cannon camera), it worked fine. Powers up in USB-power mode and charges full.

A separate minor nit: my battery came with a small connector spliced in. While gently figuring out how to orient the battery and connector in the case, the positive terminal broke loose. I ended up cutting the connector off and soldering the battery directly to the board as others have done with earlier models.

Otherwise all is well and I’m happy with my new DSO Nano.

Thx!

Dan

#40

:astonished: I am sorry that the usb cable you purchased from us had problem, and if you sure the usb cable has quality problems you can apply for a new free one .