Simple 1 second 1mA-10mA analog oscillator for green/red/white/blue LED pulsing

[eneuro]

The capacitance will be 5uF

It is enough to use eight 10uF capacitors to have an equivalent electrical circuit in the case when you do not have two non-polarized 10uF capacitors, but there are such in the SMD version, but they are probably several times more expensive than the regular polarized 10uF, and I do not have such, and it is Xmas time, so we use what we have 



Now all that's left is to design the PCB in Kicad 8 

[Analog Kid]

Any reason why you don't want to use the somewhat simpler astable multivibrator here?

[TimFox]

See page 9 ("anti-series connection" paragraphs) of this CDE application note for electrolytic capacitors for a discussion of back-to-back connection for non-polarized unit.
https://www.cde.com/resources/technical-papers/AEappGuide.pdf
This non-polarized circuit is often used in loudspeaker crossover networks, where bias voltages are not available.
The note discusses voltage ratings, especially for use in AC motor circuits.
The net capacitance for two identical capacitors in anti-series is 1/2 the capacitance of each.

[inse]

Regarding the diode circuit:
If alternating voltage is applied, each cap can be charged only once and never be discharged

[Analog Kid]

See page 9 ("anti-series connection" paragraphs) of this CDE application note for electrolytic capacitors for a discussion of back-to-back connection for non-polarized unit.
https://www.cde.com/resources/technical-papers/AEappGuide.pdf

Here, I'll save people the trouble of downloading that PDF:

If two, same-value, aluminum electrolytic capacitors are connected in anti-series configuration with the positive terminals or, more usually, the negative terminals connected together, the resulting single capacitor is a non-polar capacitor with half the capacitance. When voltage is applied to this anti-series combination, the correct-polarity capacitor gets nearly the full voltage.

[Analog Kid]

Regarding the diode circuit:
If alternating voltage is applied, each cap can be charged only once and never be discharged

OK, thanks.
You could have said that before and saved a bit of back-and-forth here.

[TimFox]

See page 9 ("anti-series connection" paragraphs) of this CDE application note for electrolytic capacitors for a discussion of back-to-back connection for non-polarized unit.
https://www.cde.com/resources/technical-papers/AEappGuide.pdf

Here, I'll save people the trouble of downloading that PDF:

If two, same-value, aluminum electrolytic capacitors are connected in anti-series configuration with the positive terminals or, more usually, the negative terminals connected together, the resulting single capacitor is a non-polar capacitor with half the capacitance. When voltage is applied to this anti-series combination, the correct-polarity capacitor gets nearly the full voltage.

I posted the site so that other people could find details about aluminum electrolytic capacitors.
Another important paragraph discusses the voltage capability of the anti-series connection:

"CDE also offers non-polar capacitors in a single can, using two anode foils and no cathode foil. Most motor-start capacitors are
also constructed this way. These are available for momentary-duty AC applications like motor starting and voltage-reversing
applications, but the high dissipation factor of aluminum electrolytic capacitors— often exceeding 2% – causes excess heating
and short life in most continuous AC applications. The reverse voltage capability is not constrained to be the same as the for-
ward voltage, as we can also create special designs that have, for example +400 VDC and -25 VDC capability. This is done by using
two anode foils with different formation voltages."

[Zero999]

The capacitance will be 5uF

It is enough to use eight 10uF capacitors to have an equivalent electrical circuit in the case when you do not have two non-polarized 10uF capacitors, but there are such in the SMD version, but they are probably several times more expensive than the regular polarized 10uF, and I do not have such, and it is Xmas time, so we use what we have 



Now all that's left is to design the PCB in Kicad 8 

That's just silly. The capacitors can easily biased, so ordinary polarised capacitors can be used. Refer to my schematic.

There's also the issue of that capacitor on the input to your LED driver just charging up, so the LEDs will stop flashing fairly quickly.

Also see #12 for a way to keep those 10uF polarised.

Creating a non polar capacitor from 2 polarized capacitors 

Welllll, maybe ...
Don't think that'll work under all circumstances, as the caps will be reverse-polarized half the time. They're not diodes.

Hey, how about this? Although you have that pesky ~0.7 volt V_f to deal with:

Yes capacitors are diodes. The diodes are just in parallel, not series. In fact, the electrolytic capacitor was originally used as a diode.
https://en.wikipedia.org/wiki/Electrolytic_capacitor?useskin=vector#Origin

Here's an equivalent circuit for two electrolytic capacitors connected back-to-back.

[Analog Kid]

Welllll, maybe ...
Don't think that'll work under all circumstances, as the caps will be reverse-polarized half the time. They're not diodes.

Hey, how about this? Although you have that pesky ~0.7 volt V_f to deal with:

Yes capacitors are diodes. The diodes are just in parallel, not series. In fact, the electrolytic capacitor was originally used as a diode.
https://en.wikipedia.org/wiki/Electrolytic_capacitor?useskin=vector#Origin

Here's an equivalent circuit for two electrolytic capacitors connected back-to-back.
(Attachment Link)

Don't want to belabor the point (a side issue in this thread), but wouldn't that suffer from the same problem as my example, the caps never getting a chance to discharge?

For some reason that one always bites me in the butt.

[Konkedout]

How about using one LM324 quad op amp?

This seems to work in LTSpice.  It is hard to beat the price of a single LM324.

[inse]

…
Don't want to belabor the point (a side issue in this thread), but wouldn't that suffer from the same problem as my example, the caps never getting a chance to discharge?

For some reason that one always bites me in the butt.

C‘mon, just think through the two phases:
+ on the left, - on the right
and then reversed polarity..
You will have nominal capacity if amplitude >> Vf

[eneuro]

Any reason why you don't want to use the somewhat simpler astable multivibrator here?

Enjoy these beautiful analog current slopes powering the LED 

[eneuro]

How about using one LM324 quad op amp?

I tested this circuit in the simulator, the power cut, i.e. negligible current consumption will be at 1.5Vcc, which is ideal in the case of powering it from many Na-ion batteries connected in parallel, while at 2.5Vcc a few more red LEDs connected in parallel will be visible at night.
The advantage of this simple oscillator in this version is that it works for a wide range of supply voltages and protects even a single Na-ion battery from complete discharge, also in the case of a single Li-ion, especially with white or blue diodes, it will be very difficult to completely discharge it.

[Zero999]

How about using one LM324 quad op amp?

This seems to work in LTSpice.  It is hard to beat the price of a single LM324.

I've put the model in the .asc so only one file is needed.

It's a ring oscillator.

[Ian.M]

Way back in 2018 I posted a squegging Joule Thief LED flasher: https://www.eevblog.com/forum/beginners/weird-one-transistor-led-blinker-circuit/msg1981934/#msg1981934   
You'll need the free LTspice simulator to open the sim I attached.
For a Joule Thief (or other boost LED drivers) LED Vf must be greater than the battery voltage.  If you are using a LiPO or Na-ion battery, you will need a few LEDs in series to meet this requirement - two for blue or white, more for other colors.  There is no undervoltage cutout so use a protected battery.

[Zero999]

Way back in 2018 I posted a squegging Joule Thief LED flasher: https://www.eevblog.com/forum/beginners/weird-one-transistor-led-blinker-circuit/msg1981934/#msg1981934   
You'll need the free LTspice simulator to open the sim I attached.
For a Joule Thief (or other boost LED drivers) LED Vf must be greater than the battery voltage.  If you are using a LiPO or Na-ion battery, you will need a few LEDs in series to meet this requirement - two for blue or white, more for other colors.  There is no undervoltage cutout so use a protected battery.

Or just connect the LED between the output and +V?

[Konkedout]

Way back in 2018 I posted a squegging Joule Thief LED flasher: https://www.eevblog.com/forum/beginners/weird-one-transistor-led-blinker-circuit/msg1981934/#msg1981934   
You'll need the free LTspice simulator to open the sim I attached.
For a Joule Thief (or other boost LED drivers) LED Vf must be greater than the battery voltage.  If you are using a LiPO or Na-ion battery, you will need a few LEDs in series to meet this requirement - two for blue or white, more for other colors.  There is no undervoltage cutout so use a protected battery.

Or just connect the LED between the output and +V?
(Attachment Link)

What I do not like about this circuit is that reverse Vbe on the 2N2222 may destroy it.  I am seeing 4V in your simulation.  Back in 1980 I had a design which had a few volts of reverse Vbe on a small signal transistor.  Even though the reverse Vbe was absolutely within the device ratings, those transistors were dying.  I fixed the problem by clamping this voltage with a 1N4148 diode added across Vbe.

Unfortunately this diode makes your oscillator run at 774 KHz,

[PCB.Wiz]

Sine we have many variants. here is one with a single capacitor timing.
It is a discrete BJT thyristor/UJT sawtooth oscillator, with optional temperature compensation, (tested at 5V) and gives a pulse drive to the LED for extended battery life.

[Zero999]

Way back in 2018 I posted a squegging Joule Thief LED flasher: https://www.eevblog.com/forum/beginners/weird-one-transistor-led-blinker-circuit/msg1981934/#msg1981934   
You'll need the free LTspice simulator to open the sim I attached.
For a Joule Thief (or other boost LED drivers) LED Vf must be greater than the battery voltage.  If you are using a LiPO or Na-ion battery, you will need a few LEDs in series to meet this requirement - two for blue or white, more for other colors.  There is no undervoltage cutout so use a protected battery.

Or just connect the LED between the output and +V?
(Attachment Link)

What I do not like about this circuit is that reverse Vbe on the 2N2222 may destroy it.  I am seeing 4V in your simulation.  Back in 1980 I had a design which had a few volts of reverse Vbe on a small signal transistor.  Even though the reverse Vbe was absolutely within the device ratings, those transistors were dying.  I fixed the problem by clamping this voltage with a 1N4148 diode added across Vbe.

Unfortunately this diode makes your oscillator run at 774 KHz,

The diode can be put in series with the base instead, but I wouldn't worry. The 2N2222 can withstand a reverse voltage of 6V, without being damaged.
https://www.onsemi.com/pdf/datasheet/p2n2222a-d.pdf

[eneuro]

There is no undervoltage cutout so use a protected battery.

Na-ion batteries can be discharged to very low voltages, the ones supplied are around 2.5V.

I added a current limit by using additional transistors, thanks to this circuit generates pulses around 1Hz in the voltage range of 2.5V-24V, you can insert several LEDs in series as a load with several batteries connected in series, but in practice this load will be several LEDs with small resistors powered in parallel from batteries connected in parallel protected by a diode to prevent current flow between cells, so it's good that it works at low voltages below 3.2V with red LEDs.

[eneuro]

It is a discrete BJT thyristor/UJT sawtooth oscillator, with optional temperature compensation, (tested at 5V) and gives a pulse drive to the LED for extended battery life.

5v is useless for 18650 cells, because to extend the battery life it is better to charge to 3.9V for Li-ion 

"Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles." https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

[Zero999]

How about using one LM324 quad op amp?

This seems to work in LTSpice.  It is hard to beat the price of a single LM324.

I've just realised six of those resistors aren't needed. Use one potential divider to get half the supply voltage and connect it to all parts of the circuit which require it.

[eneuro]

It is hard to beat the price of a single LM324.

Price is not everything  , ease of adaptation to new tasks. This is the version of my circuit in the "SMA" Sourface Mount Art  version because I use a single-sided board with a few insignificant SMD components, even holes will not be drilled, because the bottom of the PCB will be an insulator, the whole soldered in the middle of a 20mm copper pipe, filled with paraffin, because it is a very good insulator   



This PCB can be easily redesigned to fit into a copper pipe with an external diameter of 20mm, because then the 18650 batteries can be packed perfectly inside, even in a heat shrink tubing 

[inse]

And for what reason are you not going entirely SMD?
The electrolytics won‘t be nice to solder unless they hover several mm above the PCB.

[eneuro]

And for what reason are you not going entirely SMD?

This is a board for testing, now it's Xmas & New Year time, the ordered electronic components in Europe won't arrive soon, it's no problem to change the footprint in Kicad 8, which I did, because of instead of resistor R4 you can solder a cut-off piece of the resistor lead, it doesn't need to be 100R there, similarly the SMD diode D3 will be useful for testing, ultimately it's not needed, previously it was a regular 5mm LED, I can solder one for testing, because this board is easy to make using the thermal transfer method, etch in home conditions, you don't even need to drill anything.