Cut off voltage lithium battery?

[spec]

Everything with order is perfect now except that delivery costs 25£ and components around 12£.
I'm not stingy or so but that's ridiculous. Small parts like that can fit in an envelope.

Normally I order from this site https://www.electrokit.com/en/ here in Sweden but they dont have all of that parts from the list. Comparator, mosfet, diode...

I guess I'm out of options and have to proceed with mouser anyway, but it hurts

Hmm, that is annoying.

Have you checked delivery charges to Sweden from other suppliers: Digikey, Farnell, Radio Spares etc. Are there any big distributors located in Sweden.

spec

 

[audioguru]

Farnell.com lists Sweden so maybe they have a warehouse there.

 

[Rorut]

I sent an email to my local shop and they put together this list from my mouser list.
(there are some other components there for another project, the timer, a capacitor and a couple of resistors)

Hope all parts are ok? And that all the ordering hazzle I created is worth it

 

[kinarfi]

Hy Jeff,

Yes, we have designed for two different requirements. I must down load LTSPICE some time and learn how to use it.
The OP is planning on building both circuits so it will be interesting to see how they turn out.

Thanks for your info too- as i have said many times before, I always learn something new from other designers.

Chuck

I used spice to find the set point on this attachment using 'zero in' via trial & error, I find it to be an invaluable tool.

Me too, here's what I built, I'll add actual test voltages & a photo shortly

 

[spec]

I sent an email to my local shop and they put together this list from my mouser list.
(there are some other components there for another project, the timer, a capacitor and a couple of resistors)

Hope all parts are ok? And that all the ordering hazzle I created is worth it
View attachment 99452

Looks OK
spec

 

[spec]

I used spice to find the set point on this attachment using 'zero in' via trial & error, I find it to be an invaluable tool.

Me too, here's what I built, I'll add actual test voltages & a photo shortly
View attachment 99454View attachment 99471

Looks good too- very neat. Suggest putting a 100nf ceramic capacitor across the supply pins of the comparator.

It would be much easier to calculate the set point and hysteresis rather than using SPICE. It is dead easy.

spec

PS: do you get on Utah Lake much?

 

[Rorut]

Looks OK
spec

Thank you Spec. Parts ordered now
Is it possible to have an option to add a red diode when voltage cuts somewhere in circuit?
Maybe that consumes much current? Would be a nice optional feature! Thank you for all your help!

 

[spec]

Thank you Spec. Parts ordered now
Is it possible to have an option to add a red diode when voltage cuts somewhere in circuit?
Maybe that consumes much current? Would be a nice optional feature! Thank you for all your help!

No sweat Rorut.

LED indicator will be possible- will sort out.

spec

 

[spec]

Hy Rorut,

Here is the latest cut of circuit fitted with a red LED which illuminates when the battery stack voltage is above the cutoff voltage. Instead of the LED coming on when the the circuit cuts off I have implemented the reverse which is simpler to do and arguably better because it drains a low battery stack less. If that does not suit you, let me know and I will work out the opposite sense. You could also change the LED color, although a red LED will be the brightest for a given current.

The LED forward current is set to around 470uA which means that the circuit, when switched on, will now take 470uA rather than 3uA. When the circuit turns off the current will still be 4uA though. If the LED is not bright enough lower the value of R7: 10K will increase the LED current to 990uA, which should be fairly bright. 4K7 will correspond to 2.1mA which will be very bright. You could also experiment with lowering the LED current by increasing the value of R7. The formula for deriving the LED current is 9.9V/R7.

R8 prevents the LED from illuminating slightly due to any PMOSFET drain source leakage current.

Note that the eye's response to light is logarithmic, so the perceived LED light intensity will not vary as much as you might imagine. The LED current versus light output is also non linear.

spec

​

TLLK4401 Red LED Data Sheet
https://www.vishay.com/docs/83343/tlle4401.pdf

Vishay Low Current LED Range
https://www.vishay.com/leds/low-current/

Maxim MAX6008
https://datasheets.maximintegrated.com/en/ds/MAX6006A-MAX6009B.pdf

​

 

[spec]

Hy again Rorut,

Here is the cutoff circuit with both cuton and cutoff indicators- you chose.

spec

​

NOTES
(1) R15 and R19 define the current through the LEDs according to the formula I = 10.4/R. Where I is in mA and R is in K Ohms

​

 

[Rorut]

Hy Rorut,

Here is the latest cut of circuit fitted with a red LED which illuminates when the battery stack voltage is above the cutoff voltage. Instead of the LED coming on when the the circuit cuts off I have implemented the reverse which is simpler to do and arguably better because it drains a low battery stack less. If that does not suit you, let me know and I will work out the opposite sense. You could also change the LED color, although a red LED will be the brightest for a given current.

The LED forward current is set to around 470uA which means that the circuit, when switched on, will now take 470uA rather than 3uA. When the circuit turns off the current will still be 4uA though. If the LED is not bright enough lower the value of R7: 10K will increase the LED current to 990uA, which should be fairly bright. 4K7 will correspond to 2.1mA which will be very bright. You could also experiment with lowering the LED current by increasing the value of R7. The formula for deriving the LED current is 9.9V/R7.

R8 prevents the LED from illuminating slightly due to any PMOSFET drain source leakage current.

Note that the eye's response to light is logarithmic, so the perceived LED light intensity will not vary as much as you might imagine. The LED current versus light output is also non linear.

spec

View attachment 99473
​

TLLK4401 Red LED Data Sheet
https://www.vishay.com/docs/83343/tlle4401.pdf

Vishay Low Current LED Range
https://www.vishay.com/leds/low-current/

​

Awesome! Can't thank you enough!
I think your first solution will be fine or maybe both . First one looks easy to add.
Is the TLLK4401 same as this one?
https://www.electrokit.com/led-rod-3mm-lagstrom-2ma-tllr4401.42305

I have a couple of these LEDs home but it's a different model and I guess it is not suitable for this?
https://www.electrokit.com/led-3mm-rod-diffus-3500mcd.48356

I also tried to find PMV48XP with legs.
This one seems to be surface mounted?
https://www.mouser.se/ProductDetail...=sGAEpiMZZMshyDBzk1/Wi7p4QsCjHKBG/sTA52r8nkU=

 

[spec]

Is the TLLK4401 same as this one?
https://www.electrokit.com/led-rod-3mm-lagstrom-2ma-tllr4401.42305

It is low current, but not as efficient, only 0.1 of the light output for the same current. It would work, but not very well

I have a couple of these LEDs home but it's a different model and I guess it is not suitable for this? https://www.electrokit.com/led-3mm-rod-diffus-3500mcd.48356

They are good LEDS but not low current

You can check how any LED you have would look: just connect them to a 9V battery in series with a 14K nominal resistor to get around 500uA current. The formula (for a 9V supply) is, 7V/R= I, Where I is current in milliamps, and R is resistance in K Ohms. Most common LEDs give a good light output with about 5mA (1K4 Ohms) current.

I also tried to find PMV48XP with legs.
This one seems to be surface mounted?
https://www.mouser.se/ProductDetail/NXP-Semiconductors/PMV48XP215/?qs=sGAEpiMZZMshyDBzk1/Wi7p4QsCjHKBG/sTA52r8nkU=

This is the correct PMOSFET. It is in a surface mount SOT 23-3 pack, which has three small leads, but they are relatively well spaced and not too hard to solder. It is not available in a pack with leads (through hole). Incidentally you can get small adapter boards to convert small surface mount packs to through hole.

If you would like a PMOSFET in a bigger case let me know and I will see what can be done.

spec

 

[kinarfi]

Looks good too- very neat. Suggest putting a 100nf ceramic capacitor across the supply pins of the comparator.
It would be much easier to calculate the set point and hysteresis rather than using SPICE. It is dead easy.
spec
PS: do you get on Utah Lake much?

No, that would need a boat, my passion is off roading, as shown in my avatar, I'm surrounded with some beautiful mountains with lots of trails & desert and sand dunes
Jeff

 

[Rorut]

It is low current, but not as efficient, only 0.1 of the light output for the same current. It would work, but not very well


They are good LEDS but not low current

You can check how any LED you have would look: just connect them to a 9V battery in series with a 14K nominal resistor to get around 500uA current. The formula (for a 9V supply) is, 7V/R= I, Where I is current in milliamps, and R is resistance in K Ohms. Most common LEDs give a good light output with about 5mA (1K4 Ohms) current.



This is the correct PMOSFET. It is in a surface mount SOT 23-3 pack, which has three small leads, but they are relatively well spaced and not too hard to solder. It is not available in a pack with leads (through hole). Incidentally you can get small adapter boards to convert small surface mount packs to through hole.

If you would like a PMOSFET in a bigger case let me know and I will see what can be done.

spec

Goodmorning
If I want a green LED. Which one would be good?

I think I will be fine with surface mount for the PMOSFET

 

[spec]

Goodmorning
If I want a green LED. Which one would be good?

I think I will be fine with surface mount for the PMOSFET

God morgon to you Rorut.

Afraid it is wet and overcast here on the south west coast of England- but that means I wont be able to dig the garden- Oh what a shame.

I did have a quick look for a green LED originally- green generally meaning OK or on. While the human eye is most sensitive to yellow/green frequencies, that color LED is difficult to manufacture and is normally less efficient, red being optimum. I will see what can be done though.

Glad the SOT23-3 pack will be OK. It is my favorite surface mount pack because it does not take up much printed circuit real estate and is not too bad to handle, if you have a magnifier and small soldering iron bit that is.

spec

 

[spec]

Would you like a blue LED. They are considered to be very sexy these days. If so, the Vishay VLMB40L1M2-34 (where do they get these numbers from) would be a good choice: https://www.vishay.com/docs/83293/vlmb40l1.pdf
It is very bright but the problem might be that it is surface mount. It looks quite easy to solder though.

If you really wanted a green LED, it would only have one tenth of the luminosity, but you could try the Vishay TLLG4401 which is through hole. https://www.vishay.com/docs/83029/tllg440.pdf

spec

 

[Rorut]

God morgon to you Rorut.

Afraid it is wet and overcast here on the south west coast of England- but that means I wont be able to dig the garden- Oh what a shame.

Hehe, sounds like normal weather in Gothenburg, excluding today. Summer came a couple a days ago with 24C

Would you like a blue LED. They are considered to be very sexy these days. If so, the Vishay VLMB40L1M2-34 (where do they get these numbers from) would be a good choice: https://www.vishay.com/docs/83293/vlmb40l1.pdf
It is very bright but the problem might be that it is surface mount. It looks quite easy to solder though.

If you really wanted a green LED, it would only have one tenth of the luminosity, but you could try the Vishay TLLG4401 which is through hole. https://www.vishay.com/docs/83029/tllg440.pdf

spec

I would like to try both blue and green. Would be nice with green/blue when load is on and red when it cuts off.
Thanks for the links spec!

 

[spec]

Hehe, sounds like normal weather in Gothenburg, excluding today. Summer came a couple a days ago with 24C

I would like to try both blue and green. Would be nice with green/blue when load is on and red when it cuts off.
Thanks for the links spec!

The weather turned sunny and hot in the afternoon. So I accompanied Mrs spec for some light shopping in town followed by lunch at a pub in the country.

No prob about links- I now know a bit about low power LEDs thanks to you.

Are you saying blue on and red off- that is what I would advise. If so I would also advise that you go for a surface mount red LED to match the surface mount blue LED. Those tiny surface mount LEDs look particularly good.

The Vishay VLMS30K2L2 surface mount red LED should match the surface mount blue LED.
https://www.vishay.com/docs/81322/vlmosy30.pdf

spec

 

[Rorut]

The weather turned sunny and hot in the afternoon. So I accompanied Mrs spec for some light shopping in town followed by lunch at a pub in the country.

No prob about links- I now know a bit about low power LEDs thanks to you.

Are you saying blue on and red off- that is what I would advise. If so I would also advise that you go for a surface mount red LED to match the surface mount blue LED. Those tiny surface mount LEDs look particularly good.

The Vishay VLMS30K2L2 surface mount red LED should match the surface mount blue LED.
https://www.vishay.com/docs/81322/vlmosy30.pdf

spec

Sounds very good. Is it possible to mount thoose on a panel somehow? Im using small metallic led holders for 3mm leds in my panel. Maybe I can glue them behind the holders or something.
I didn't know about low power LEDs before. Quite a difference 2ma compared to ordinary led consuming 20ma. I now need to replace leds in other places as well

 

[spec]

Hmm. Good question about mounting surface mount LEDs.
All I can suggest, without getting too fancy, is to drill a small hole in your front panel and, as you say, glue the surface mount LEDS behind.
Yes, low power LEDs are useful. From what I have found Vishay seem to produce versions with a good performance.

spec