1220 yes. Mine came with a battery, but I've heard that the Chinese kits often ship without a battery now. It's a shame.

You're welcome. I use this as the sound system on my desktop PC now, and I think also that it sounds good for such a small amp.

Check that the power is reaching the amplifier chip - you can see the pin out for the chip in the datasheet linked in the description.

Thanks!

Interesting. I wondered if the negative side was needed to drive a power rail for op-amps in the mixer.

It's a while ago now, but as I remember it doesn't have any kind of memory when it is switched off.

From what I remember, a few pins have a diode, such that when the matching Q pin on the central unit goes low, the diode can switch on and it is a path to ground. Since only one of the Q pins is high at any time, there's a fairly good chance that you'll get a ground connection unless of course all the wires in the cable that correspond to the diodes are broken.

He switched to AC. Perhaps he should've left it on DC?

Mine doesn't have a slot, so I'm not sure. Is it a vent to allow heat out?

In the Arduino code? Yes, you can make a locking button through code.

I have manage to do it. Your video was very helpful. The electrician made the installation wrong and now the led behind the back of the bedroom bad is without a switch. I will turn it on/off via Arduino when the led on the ceiling is on respectively off. ​Edit: I have made the comment on the wrong video but yours was the video that helped me to solve my problem. @@MartynDavies

I would probably check the corresponding pins of the 4017 to make sure that it's not shorted, and can provide a high output.

@@MartynDavies ok thanks, already is fixed. Now works properly

This looks similar: www.aliexpress.com/item/1005006246787123.html

in the video I do this at 21:37

I don't understand sorry

Ok I ll find it now thanks❤

@@Legend813a Thanks

I'm not sure where this box is now (this was some years ago), but I would guess R1/R3 = 1k and R5/R6 perhaps 68k. The transistor type won't be crucial, I think any general purpose NPN would be fine, e.g. BC107, S8050 etc.

​@@MartynDavies Hi sir i am so glad to your reply thank you , i will take this values and references into account, Best Regard !

I was interested from early on in electronics, and had the good fortune to be around when the 8-bit micro computers were in their hayday (the 80's). In the 70's/80's there were several monthly magazines aimed at electronics hobbyists, and (hard to believe now) many people worked on electronics stuff in their spare time. I spent a lot of time combining my love of electronics and computers, connecting memory boards, sound chips, home-made controller/paddles etc, and learned a lot this way. My degree had some electronics in the programme, but I was a Computer Science major and gradually dropped the electronics modules in favour of topics like the "C" language. I have done some embedded work during my career (I'm really a software engineer), but mainly the work these days is about The Cloud/APIs/devops etc rather than low-level stuff.

I can't remember exactly what process I used, as this was quite a few years back. However, it's often possible to reverse engineer a board by buzzing it out with a multimeter/continuity tester, to know which chip outputs go to the LEDs. Usually these 7-segment displays are wired with a common anode/cathode, i.e. all the 7 LEDs (or 8 if it has a decimal point) are connected at one end meaning that all earths (for common cathode) come to the same pin, and so connecting that pin to ground is effectively an 'enable' for the whole 7/8 segments. So with four displays you have 4 enable pins. So then it's just a question of knowing which 8 anode pins connect to which 74595 pins, and where the 4 enable pins connect to the 74595. Also, there are a lot of these low-cost displays using the 74595 chip: some are 7 segment, some 8x8 dot matrix etc, and there are a lot of schematics on the Internet that people have drawn to illustrate how they are wired up, plus there are a lot of open-source code examples (e.g. for the Arduino or Raspberry Pi) showing how to drive these displays. I may have just messed around in the code to see what lit up when I clocked some bits into the display, since I love to experiment with code. As to your question: the 74595 doesn't care which bits are the digit and which the row selector - it will just store and present the 16 bits that we clock into the chips and then latch. The magic of which 4 bits are the row selector is all down to the way that we interconnect the 74595 pins with the LED display pins, and this will often be different depending on the style of display we're using.

This is a good place: simcom.ee/documents/?dir=SIM800. You'll find the AT command set guide and the hardware design manual there, which are both good references.

Google Translate? Yes, I believe it still is. Call up the Play Store and it will tell you.