Recent Posts

1

Microcontrollers / Re: Can't disable alarms on DS3231 RTC module

« Last post by Peabody on Today at 02:58:05 am »

The only time you disable the alarms in your code is immediately followed by setting alarm1 again.

Code: [Select]

    rtc.disableAlarm(2);
    rtc.disableAlarm(1);

    // schedule an alarm 10 seconds in the future
    if(!rtc.setAlarm1(
            rtc.now() + TimeSpan(10),
            DS3231_A1_Second // this mode triggers the alarm when the seconds match. See Doxygen for other options
    )) {

ClearAlarm only clears the alarm flag, letting the INT pin go back high.  It doesn't disable the alarm.

2

Beginners / Re: 555 driver and Transformer questions

« Last post by Xena E on Today at 02:52:27 am »

Xena, you are close, 80 year old technology.
I did incorporate potentiometers in parallel to the two. I also used one to both resistors with the center to pin 7 in order to try balancing both sides in one shot.

Even though potted I was able to check all components from various taps. Some the resistors have wandered off. Of all the units I played with only one had a bad capacitor.

I will try the resistor from pin 3 and look into the bipolar with zener, unless anyone has a suggestion where to start with a circuit, or for me to read up on it.

So, I've drawn up  a quick sketch of something that you may be able to develop: principally sound but it may need tinkering to work.

I'm not saying the use of a MOSFET isn't possible it could work OK, but its trying to work in follower mode, series diode as suggested by Circlotron is a first option. This is just something else to try.



PNP transistor to replace the contacts, that being protected by the Zener snubber, the transistor is WHY? But of course there will be an Ic consideration and the induced voltage should be limited to around ×10 of the supply, so choose the transistor and Zener appropriately, with the transistor Vce higher than the Zener voltage of course. The drive to the transistor must also be able to swing near enough to the + supply to switch it off.

I built an ignition unit for a friend who has an old Fordson gas/kerosene tractor that used a similar arrangement. the transistor was a TIP 3055 (6volt + ground, so circuit inverted, and a Kettering ignition coil as load, it survived for over two years with a 56 Volt 1W Zener for protection)

It may also be possible to just use a series capacitor/resistor combo across the primary but without the actual coil in front of me the component values would be pure guesstimate.

I'd be inclined to start with the transistor drive "low" (on time) short, and increase from there watching for activity from the tube heater.

Normally setting this kind of circuit up is a bit tricky if you don't know what HVDC voltage you're aiming for, though if all else fails the heater power of the tube can be determined using a lamp/LDR combination.

Regards,
Xena.

3

General Technical Chat / Re: H5N1 bird flu and how we're risking another global pandemic

« Last post by CatalinaWOW on Today at 02:49:50 am »

Sustainable farming will only support a sustainable human population.  Which may take a pandemic to achieve.

Factory farming uses so much land (if everything is properly counted) that even "conventional" farming would be much more sustainable.

Traditional farming is sustainable.  But look at food yield per acre on various types of land using this type of agriculture (there is only a little of the very good stuff, lots of OK stuff and huge amounts of very marginal land.  Be sure to make sure that water sources are sustainable.  Then see what population it will support.  Even if we go all vegetarian.  Be sure to use solid sources for the calculations.  The posts of meat eaters and vegetarians both wildly miscount the real needs to support their preferred diet. 

4

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by KungFuJosh on Today at 02:41:03 am »

A "mini-lathe" or "mini-mill" are rightly regarded by the professional as toys compared to the 250K 8,000 lb. behemoth - but those "toys" may be the far better choice for the hobby user, and the hobby user might actually be producing superior work - in terms of precision, or in terms of beauty, or so on - because that is what the hobby user is focused on, without being constrained by the demands of the clock.

I disagree with this analogy. Professionals look for quality, size is not relevant in that way.

from what i observed, not everytime. pro usually look for time saving, quality maybe "okayish" or "acceptable", but anyone who look for quality will need more time. this what imho make apart name like Porche or Lamborghini with like Ford or Tesla.

You're right, of course, but we're talking about different types of professionals now. Contractors or laborers vs. specialty stuff like furniture makers, or artiiiists. Some furniture people buy chisel sets that cost more than a full DeWalt set of contractor power tools.

These analogies are getting out of hand lol.

5

Power/Renewable Energy/EV's / Re: TPS61021A boost regulator can't handle 50mA

« Last post by __steven on Today at 02:39:41 am »

Caleb, can you confirm that the PGND pad is indeed connected to ground in your layout (I believe this is pin 9)? I cannot tell from the photograph. Alternatively, have you attempted reflowing the IC such that you can validate that the PGND pad is making a good connection to the pad? I have had IC's that use this pad as an internal reference act funny when the part is not correctly soldered. It should dance under waving hot air.

Steven

6

Jobs / Re: Contract work

« Last post by Mark Chips on Today at 02:39:24 am »

Do you have any ideas as how to proceed with what I need?

7

Projects, Designs, and Technical Stuff / Re: Passing 2 wires into a hot water cylinder

« Last post by zapta on Today at 02:38:22 am »

Have you consider thermowells  They come in many shapes, with or without threads, are hollow, and allow to insert temperature sensors from the outside, keeping the sensor dry.

https://duckduckgo.com/?q=thermowell&iax=images&ia=images

8

Test Equipment / Re: OWON HDS 200 Handheld Oscilloscope w/ builtin DMM/AWG

« Last post by Anthocyanina on Today at 02:23:59 am »

The low battery message when the battery is still far from low is very annoying, i tried powering the scope from a bench supply,but all i get is some quiet clicky noises. the supply is set at 4V, and with current limits from 100mA to basically unlimited, this behaviour doesn't change. i don't understand what's going on, because with a single battery installed it turns on fine, and if i connect a battery and the power supply, then remove the battery, it stays on for a few seconds after battery removal and then switches itself off. could anyone try to power this scope with a bench supply and see what happens?

Thank you!

9

Projects, Designs, and Technical Stuff / Re: Need help designing and choosing an ADC!

« Last post by zapta on Today at 02:21:51 am »

Is this for a loadcell?

Last year I designed an interface for high rate high accuracy load cell.  The schematic is below. It was a plugin board with 3.3V SPI interface and 5V supply rail.  It also has three thermistor/PT1000 inputs which you can drop.  For low noise you want to excite the loadcell and the recommended voltage (e.g. 10V) since its output is linear with the excitation voltage. The board also has an optional Kelvin topology to reduce the error due to the excitation current voltage drop.

https://github.com/zapta/daq/blob/main/adc/kicad/adc.pdf

10

Test Equipment / Re: Standardised Way To Test Oscilloscope Screen Update Rate

« Last post by bdunham7 on Today at 02:21:46 am »

I like pdenisowski's "pixels changing" definition, so any test source need to have "pixels changing" at a fast enough rate to make the measurement possible.

You'd just have to ensure that the waveform rate was higher than the screen rate so that you'd expect new information to be available at every screen refresh.

What is bit  confusing about the video I posted is that the waveform update is set at 60/s (using line trigger) and the 60fps video shows a display update (pixel change) on each and every frame yet there are multiple traces showing.  This is why I was saying that 'screen rate' or 'screen update' may not be simple, clear-cut concepts.