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by Z80 Refugee
Tue Jun 05, 2018 10:49 pm
Forum: Automation, sensing and robotics
Topic: Relay Module KY-019 5V
Replies: 488
Views: 85408

Re: Relay Module KY-019 5V

Apart from that isolation these type of boards usually have bare contacts, and tracks on the switch contacts very close to other tracks on the board so be very careful!! Just because a relay has a mains voltage printed on it as contact rating, doesn't mean it meets European/British directives for e...
by Z80 Refugee
Tue Jun 05, 2018 10:45 pm
Forum: Automation, sensing and robotics
Topic: Relay Module KY-019 5V
Replies: 488
Views: 85408

Re: Relay Module KY-019 5V

tlfong01 wrote:
Tue Jun 05, 2018 2:07 pm
The schematic is indeed weird, and the transistor should be inverted. I have redrawn the schematic as attached below.
This time you have the LED the wrong way around.
by Z80 Refugee
Tue Jun 05, 2018 9:45 am
Forum: Automation, sensing and robotics
Topic: Relay Module KY-019 5V
Replies: 488
Views: 85408

Re: Relay Module KY-019 5V

A word of caution with relays used to switch mains power. If they don't include opto-coupling insulation (and maybe even if they say they do) I would strongly suggest that they should be controlled through an opto-coupler and not directly a GPIO or transistor. Opto-isolation adds an extra level of ...
by Z80 Refugee
Tue Jun 05, 2018 7:52 am
Forum: Automation, sensing and robotics
Topic: Relay Module KY-019 5V
Replies: 488
Views: 85408

Re: Relay Module KY-019 5V

So I found the schematic, though 4 years too late! That schematic is poor. For one thing: if the transistor were fitted the way it is shown, the circuit wouldn't work. Without specifying the transistor type (what, exactly, is an "8050"?), it is not possible to verify the component values appropriat...
by Z80 Refugee
Mon Jun 04, 2018 6:48 am
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

A digital multimeter averages the input over the sample period (typically a few tenths of a second), as a consequence of its measurement process. An analogue meter averages the input due to the low pass filter response of its mechanical nature. Neither will provide useful data for this kind of thing...
by Z80 Refugee
Sun Jun 03, 2018 9:26 am
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

Getting back to the OP's original problem, the cure was to shorten and beef up the cables from the power source. That then revealed a subsequent problem with the power source being unable to sustain peak load (it crosses my mind that winding the output voltage up actually makes the problem worse - m...
by Z80 Refugee
Sun Jun 03, 2018 8:51 am
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

There is a great deal of presumption going on regarding the formal voltage specifications for the RPi - and I can't find any. So why did you presume 5V1? I thought I read it somewhere - you know what it's like when there is no published specification, and that's why I labelled the RPi a "toy"* in a...
by Z80 Refugee
Sat Jun 02, 2018 11:25 am
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

Like I said before - try it. I know which horse my money is on.

There is a great deal of presumption going on regarding the formal voltage specifications for the RPi - and I can't find any.
by Z80 Refugee
Sat Jun 02, 2018 8:31 am
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

Yes, I'm a retired electronics design engineer with military, automotive, and high-reliability systems experience. I stand to be corrected, but my vote is that the cap-res-diode circuit won't work. Even with a Schottky diode, the forward voltage will be about 0.3V (or more, unless the current is ver...
by Z80 Refugee
Fri Jun 01, 2018 9:37 am
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

I assume you mean your circuit has been shown to work in practice then. If so, I take it back. Some 'scope plots demonstrating its performance would be nice...
by Z80 Refugee
Fri Jun 01, 2018 9:29 am
Forum: Beginners
Topic: Raspberry lifetime
Replies: 23
Views: 1902

Re: Raspberry lifetime

That's good, and I'm very pleased if compliance documentation becomes available - that will certainly qualify the RPi for use as a component in critical systems. My point was not to degegrate the RPi, but to explain the considerations that are required before specifying anything for use in potential...
by Z80 Refugee
Fri Jun 01, 2018 9:24 am
Forum: Troubleshooting
Topic: Maximum voltage draw from B+, what is safe?
Replies: 8
Views: 1003

Re: Maximum voltage draw from B+, what is safe?

No. I'm not talking about the data bus, I'm talking about the power rails. As far as I can see, there is nothing internal to the RPi (apart from the converter/regulator) that uses 5V except the red LED. There are 5V outputs on the GPIO, USB, and HDMI. If you don't believe me, take a look at the sche...
by Z80 Refugee
Thu May 31, 2018 3:17 pm
Forum: Beginners
Topic: Raspberry lifetime
Replies: 23
Views: 1902

Re: Raspberry lifetime

Just because it has been pressed into service by "professionals" doesn't make it a product designed for professional use. When I design a product, either my customers demand guarantees of its performance or I have to decide what guarantees to offer, which apply over the warranted life of the product...
by Z80 Refugee
Thu May 31, 2018 3:01 pm
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

Imperf3kt wrote:
Thu May 31, 2018 2:14 pm
I did find some 100uf caps though, is this maybe getting too low?
Try it and see - you never know. You could always fit several.
by Z80 Refugee
Thu May 31, 2018 3:00 pm
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

In what way is it that? If you are aware of that circuit configuration actually being used in practice to combat supply voltage drops due to instantaneous demand, please refer me to an example. The circuit is suitable for maintaining a supply rail (at reduced voltage) temporarily to, for example, a...
by Z80 Refugee
Thu May 31, 2018 8:28 am
Forum: Beginners
Topic: Raspberry lifetime
Replies: 23
Views: 1902

Re: Raspberry lifetime

I don't think the Pi is a "toy" any more than any other mass produced device based around an ARM SoC is. Okay, what term would you prefer me to use: a product designed for hobbyists rather than the professional market? If it were intended for professional applications it would need many more publis...
by Z80 Refugee
Wed May 30, 2018 8:56 pm
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

How about putting a resistor in parallel with a schottky diode, in series with the capacitor? On power-up, the cap charges through the resistor (the diode is reverse-biased) so does so slowly. When power disappears momentarily, the cap supplies current through the diode. screen,b60.png Professional...
by Z80 Refugee
Wed May 30, 2018 4:16 pm
Forum: Beginners
Topic: Raspberry lifetime
Replies: 23
Views: 1902

Re: Raspberry lifetime

The real answer is: nobody knows. After the initial burn-in period, failures are random events measured in terms of MTBF (Mean Time Between Failures) - which boils down to an average number of units that are expected to fail out of (say) 1 million units in any period (say 1 year). Unless those figur...
by Z80 Refugee
Wed May 30, 2018 3:56 pm
Forum: Troubleshooting
Topic: Maximum voltage draw from B+, what is safe?
Replies: 8
Views: 1003

Re: Maximum voltage draw from B+, what is safe?

I'm not using any phone charging cables. Never said you were. I was just explaining. The cable I was using with the bench power supply was too thin and quite long. Swapping out the cable has resolved this issue. :roll: I would still like to know if there would be a performance drop in the CPU maxim...
by Z80 Refugee
Wed May 30, 2018 10:28 am
Forum: Advanced users
Topic: Isolated CPU Frequency measurement based on instructions?
Replies: 5
Views: 567

Re: Isolated CPU Frequency measurement based on instructions?

Take a look at the design specifications for an ARM processor - you will find it is a very much more complicated beast than your average microcontroller. I don't think this approach will yield any useful result.
by Z80 Refugee
Wed May 30, 2018 10:21 am
Forum: Troubleshooting
Topic: Maximum voltage draw from B+, what is safe?
Replies: 8
Views: 1003

Re: Maximum voltage draw from B+, what is safe?

First: nothing "draws" voltage. Voltage is the supplied "pressure" from which current is drawn. This basic error leads me to suspect you don't really know much about what you are trying to do (that's not meant to be taken as an insult, only to point out you may be out of your depth). The required cu...
by Z80 Refugee
Wed May 30, 2018 9:40 am
Forum: Advanced users
Topic: Brief voltage drop on UPS like system. would a capacitor fix it?
Replies: 53
Views: 6098

Re: Brief voltage drop on UPS like system. would a capacitor fix it?

This is the inrush current I was talking about. It overloads your regulator which then shuts down. The easiest option is to try a smaller capacitor.

You may have to accept that your chosen regulator is not up to the mark.
by Z80 Refugee
Wed May 30, 2018 9:00 am
Forum: General discussion
Topic: HDMI sends frequency radiation
Replies: 3
Views: 506

Re: HDMI sends frequency radiation

That's what HDMI is - a serial digital signal at that kind of frequency. Any source of HDMI does the same, and I have seen many cases where a PVR outputting HDMI to a TV blanks out the incoming aerial signal. Your 708MHz suggests to me you are operating the HDMI at 1080p. Changing that to 1080i shou...
by Z80 Refugee
Tue May 29, 2018 12:59 pm
Forum: Beginners
Topic: Raspberry pi 3 b+ with powerbank
Replies: 19
Views: 10928

Re: Raspberry pi 3 b+ with powerbank

as I can figure out, inside the case there are 2 separate batteries, right? Yes. So what? They are not used separately by the power bank. So I can use the one battery to supply the Raspberry and a few sensors, and the other battery to supply the other sensors, right? What gives you that idea? The t...
by Z80 Refugee
Tue May 29, 2018 10:16 am
Forum: Beginners
Topic: It is possible to connect 3 external hard drives?
Replies: 7
Views: 485

Re: It is possible to connect 3 external hard drives?

Some drive enclosures get 12V from the 'brick' but rely solely on the USB interface for the 5V portion . I didn't know that; thanks. They are aroud 0.6a 5v anda 0,7a 12v each. 3 x 0.6A = 1.8A, which is more than the RPi can supply. This seems to support klricks' observation. The solution is to use ...

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