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Stayin Alive with the 555

scottiebabe — Wed, 05 Oct 2022 01:19:29 GMT

Many individuals have created a version of this circuit before. So, I take no credit.

Most USB power banks have an auto shutoff feature that is triggered when the output current drops below a threshold value. I am guessing whatever value that is, will vary greatly from unit to unit so you may need to adjust the load resistors.

This circuit kept my dollar store power bank from going into auto shutdown.

The oscillation frequency was approximately 1/7 Hz.

So every 7 seconds a ~100mA load is applied for ~100 ms.

The advantage of a pulse load circuit like this is that the average load current can be kept low, instead of say a static 100 mA load on your power bank.

RE: Stayin Alive with the 555

scottiebabe — Tue, 18 Oct 2022 17:31:55 GMT

Even more terrifying is the thought of a python script regulating a boost converter ☠

Very Scary!!!

RE: Stayin Alive with the 555

rsjawale24 — Thu, 06 Oct 2022 17:57:37 GMT

umm I guess you need to take care about the loading effect when connection the 555 with the power bank IC. Maybe due to the impedance differences there is a drop in the amplitude. I'm not very sure though.

RE: Stayin Alive with the 555

scottiebabe — Thu, 06 Oct 2022 17:26:25 GMT

Another power bank I have is based on the IP5305 and the datasheet would suggest my original circuit should work:

https://aitendo3.sakura.ne.jp/aitendo_data/product_img/ic/charger/IP5305/IP5305-Injoinic.pdf

However no luck. I needed both a larger amplitude and duration to keep this power bank alive.

The morale of the story is that, some breadboard experimentation is required to see what your power bank needs to see to stay alive...

RE: Stayin Alive with the 555

scottiebabe — Thu, 06 Oct 2022 12:58:40 GMT

The control IC in my USB power bank is a TP4333:

On my powerbank the SWT pin left NC (there is no button or flashlight).

Unfortunately there are no detailed specifications on the auto shutdown feature:

https://www.skytech.ir/DownLoad/File/1167_ETP4333.pdf

RE: Stayin Alive with the 555

Jan Cumps — Wed, 05 Oct 2022 18:32:24 GMT

The LED is pumpkin-coloured

RE: Stayin Alive with the 555

scottiebabe — Wed, 05 Oct 2022 18:07:47 GMT

LOL it does look a lot like a dead spider 🕷. It is also a power parasite, that keeps saying Boo! every 10s to the power bank.

RE: Stayin Alive with the 555

scottiebabe — Wed, 05 Oct 2022 18:05:26 GMT

That's very cool! That keithley has much better precision/accuracy and dynamic range than a DS1054!

To make measurements like that I have to measure the idle/sleep current separately and then stitch everything together in Matlab...

RE: Stayin Alive with the 555

javagoza — Wed, 05 Oct 2022 17:32:05 GMT

Two more days adding hardware and you already have a monster for the Halloween competition 👻

RE: Stayin Alive with the 555

Jan Cumps — Wed, 05 Oct 2022 17:27:07 GMT

For the Keithley DMM6500, I've written a custom App (what a time to be alive. Lab instruments support Apps) that collects the AmpHours used by an application over time. If the supply voltage is a given constant, it can also calculate the WattHours.

RE: Stayin Alive with the 555

scottiebabe — Wed, 05 Oct 2022 16:47:46 GMT

Yes! This is great advice. Perhaps I will add another plot. Although the quiescent current of the bipolar 555 is nothing to get excited about. If only I had some CMOS 555s....

RE: Stayin Alive with the 555

scottiebabe — Wed, 05 Oct 2022 16:46:08 GMT

Its the circuit has kept a small amber LED running at 2 mA for some time now!

RE: Stayin Alive with the 555

Jan Cumps — Wed, 05 Oct 2022 16:08:14 GMT

You can use the integrate math function of your scope to calculate the total current consumed by the pulses over a time period.

RE: Stayin Alive with the 555

scottiebabe — Wed, 05 Oct 2022 15:50:56 GMT

Here is the load current of the 555 load pulser:

I used 2 10uF MLCC capacitors as the timing capacitor, which have a poor tolerance and strong voltage coefficient. So, the actual timing of the circuit is pretty loosely specified. But so are the specs needed to keep the power bank awake...

The Vol of the bipolar 555 is approximately 2V:

So If I really wanted a 100 mA load pulse I should use a 30 Ohm load resistor. Or perhaps 50 ohm resistor in parallel with a 100 ohm resistor would be close enough...