Home DIY Electronics

Matt H's Comment

Wed, 15 Apr 2026 06:07:15 +0100

What Mhz frequency limit does the oscilloscope have? If it's going to be a 100Mhz or 200Mhz scope, I think I would like to build one.

Paul Roth's Comment

Fri, 30 Jan 2026 23:10:02 +0000

Thank you for taking the time and interest to share insights and encourage budding electronics practitioners.

stacyj's Comment

Tue, 30 Dec 2025 19:03:12 +0000

Hello Steve--
I'm Stacy Johnson from North Dakota, USA.
I related to several things in your "about me" post. The main thing i wanted to say was Thank You for this offering for the netizens. I wish I'd found it earlier!
Hope your Christmas was merry and your new year even better.
Stacy

Rod Agno's Comment

Mon, 05 May 2025 02:27:09 +0100

Realy cool stuff. Can the circuit be modified to have only one LED light up at one time such that the LED is proportional or indicative of the pot position or resistance? Many thanks...

Surya Rai's Comment

Sat, 14 Dec 2024 03:17:34 +0000

Good trick, thanks

Jack's Comment

Thu, 19 Sep 2024 19:16:00 +0100

How to disable the extended time during the duration of one cycle. If the duration is set to 1 minute, pressing the button several times during the cycle will continue the countdown without extending the time.

Wtorres's Comment

Fri, 28 Jun 2024 18:31:23 +0100

Translation!!

It's just what I need!! The only thing I had to add is a 100 ohm resistor in series to the potentiometer to protect the 555 in case the potentiometer reaches zero ohms

Wtorres's Comment

Fri, 28 Jun 2024 18:29:17 +0100

Es justo lo que necesito!! Lo único que tuve que agregar es una resistencia de 100 ohmios en serie al potenciómetro para proteger el 555 en caso de que el potenciómetro llegue a cero ohmios

G Meier's Comment

Wed, 12 Jun 2024 19:05:06 +0100

I measured on a transformator, 230V AC, the voltage on the second winding, 30V AC, but
my soundcard oscilloskop showed a SQUARE output! No SINUS-wave... I expected
a sinus wave of cause. The square wave was not fifty fifty. Duty about 70% on
and 30% off. What the hell...

Mr candice's Comment

Fri, 17 May 2024 06:05:58 +0100

That resistor tasty tho

Ravindran's Comment

Mon, 26 Feb 2024 14:41:19 +0000

I have assembled the circuit and working verywell. Tested upto 3 Hrs with 2200micro frad capacitor.
Used pnp transister Bc557 connected to out put of pin 3 with relay drive. I need one clarification. One end of the capacitor is connected to base of transistor Bc547. Pl clarify how discharge of capacitor is taking?

Ravindran's Comment

Mon, 26 Feb 2024 14:07:34 +0000

Ravindran's Comment

Mon, 26 Feb 2024 13:49:25 +0000

I have assembled the circuit and working verywell. Tested upto 3 Hrs. Used pnp transister Bc557 connected to out put of pin 3 with relay drive. I need one clarification. On end of the capacitor is connected to base of transistor Bc547. Pl clarify how discharge of capacitor is taking?

Marks's Comment

Fri, 22 Dec 2023 00:53:56 +0000

This is just a test to see if I can hack into this system. >:-}

Tom's Comment

Tue, 12 Dec 2023 23:45:09 +0000

As to the battery question, it looks like one nine volt battery with the + connected to the top (+) and the - connected to the ground which is marked -ve.
Regarding the 10,000 ohm potentiometer question the typical potentiometer has three terminals. The center terminal is shown in the center and is connected to the hollow o by an arrow. This terminal is where the knob changes the resistance relative to the two other terminals. (I realize it has been years since this question was asked but this answer may help someone.)

Tony Castles's Comment

Fri, 10 Nov 2023 16:51:42 +0000

Did you use any CAD layout software? I am trying out VeeCAD and Fritzing to generate a construction picture like your 'Pro-Mini carrier board'

G.Smit's Comment

Sat, 29 Apr 2023 09:52:29 +0100

Ik weet het nog niet.

Natasha Young's Comment

Tue, 10 Jan 2023 02:35:46 +0000

I am a newbie to electronics and I love this post as I am also renovating my house to be fully automated but on a budget. I am learning how to use an Arduino as my starting projects and have 2 great starter kits. I'll be reading up on your site now so thank you from a wannabe :)

GP's Comment

Thu, 10 Nov 2022 03:19:51 +0000

I've wanted to have a scope show NTSC video on screen in a raster but never tried it. Now retired don't have access to a scope. It would be nice to add a Z access to this program for showing an image. would probably use the Mic input. I can make a rectangle show using square wave from the generator but see where people make sync separators and create sawtooth signals. A few places I had access to nice signal generators. Was always too busy to play around. Thanks for this program.

Kim's Comment

Thu, 11 Aug 2022 16:31:44 +0100

amazing post of interrupt and operating ultrasonic module. great help for my advanced project! thx a lot

Kevin Crossland's Comment

Sat, 02 Jul 2022 20:09:16 +0100

Definitely need a multimeter in there too!

shadin's Comment

Tue, 25 Jan 2022 03:50:11 +0000

Nice article. I read it several times but could not find the details regarding the running pin GPIO 19.

Paul's Comment

Wed, 02 Jun 2021 06:29:09 +0100

Agree with you but personally I would not use it for longer the 1 hour and only if the accuracy is not critical. But the 555 can be very use full. I sometimes will use them as a gate driver or just for its high current output. It is cheap and I always have a few in the bin.

Paul's Comment

Wed, 02 Jun 2021 06:14:22 +0100

If Current is not a problem and you are working from any supply above 5V with a added regulator to the attiny ext a LMC555 or 7555 would probably be much cheaper and will take much less time. May be for the same or smaller PCB depending on your PCB layout abilities.

best guide's Comment

Tue, 11 May 2021 19:48:44 +0100

wonderful review article. This is the most important site to me. Very informative and help resource.

Biomedical engineering project's Comment

Wed, 03 Mar 2021 06:54:36 +0000

nice information

david johns's Comment

Sat, 23 Jan 2021 09:32:33 +0000

Great and awesome post! I appreciate your efforts on writing.

Ranjith Seneviratne's Comment

Sun, 17 Jan 2021 12:24:03 +0000

I am not good in electronics, please explain clearly

Matthew's Comment

Sun, 06 Dec 2020 18:01:22 +0000

Hello,
I need some help with trying to get a Raspberry pie UPS but that can also supply 12v to keep a router a live.
can you suggest anything?
Thanks

If I understand you correctly, you want a UPS to provide both 5v for your Raspberry Pi & 12v for your router.
I have seen dual voltage buck converters on the market. If you don’t want to go that route, you could buy a pair of single voltage buck converters and use them in parallel from the same battery-protected circuit. But to do so, you’d need to supply battery voltage above 12v - somewhere in the 15v range should be minimum to ensure your buck converter will work properly. You could do this with 12 NIMH AA batteries in series. You will also need an AC—>DC power supply capable of outputting 18+ volts to maintain forward bias on the diodes. An old laptop power supply might work well for you. You’ll also need to modify/verify all your components to work with the higher voltages, too.

OOOORRRRR... you could go the easy route.
You could spend $40-75 on a commercial UPS which would back up several devices at the same time. APC, CyberPower, Tripp Lite, etc. make these battery backup units which are designed for that purpose. They tend to last 3-5 years before you have to replace the lead-acid battery inside (or just buy a new one). That’s the path I would take if I were you.

But whichever path you choose, I wish you luck.

Antonio's Comment

Thu, 03 Dec 2020 11:28:03 +0000

Hello,

I need some help with trying to get a Raspberry pie UPS but that can also supply 12v to keep a router a live.

can you suggest anything?

Thanks