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Search: Posts Made By: Radio Fox
Forum: General Electronics Technical Discussion 09-30-2018, 08:07 AM
Replies: 11
Views: 987
Posted By Radio Fox
Re: September equipment offer (u.k.)

If you click on the link in your first post & scroll down, it's shown in the associated products. Order code SD02162.


...
Forum: General Capacitor Questions & Issues 09-30-2018, 04:33 AM
Replies: 1
Views: 281
Posted By Radio Fox
Re: SMD Ceramic Componet Identification and Voltage question.

Capacitors can be used anywhere in a circuit. They are not only used for decoupling or smoothing (in which case one side would normally be grounded), but for timing, coupling etc.

Take a look at a...
Forum: General Electronics Technical Discussion 09-30-2018, 04:20 AM
Replies: 11
Views: 987
Posted By Radio Fox
Re: September equipment offer (u.k.)

Pretty fast delivery too. Arrived within a few days.

I ordered the spares kit with mine. Only cost 2.40, so thought it was worth getting at the same time to save on postage.

Havent used it...
Forum: General Electronics Technical Discussion 09-15-2018, 11:38 AM
Replies: 11
Views: 987
Posted By Radio Fox
Re: September equipment offer (u.k.)

Thanks for the link.


I've been looking around for a desoldering station, so this has come at just the right time. I see that the previous price was 84 (inc VAT). Still cheaper than Ebay &...
Forum: General Electronics Technical Discussion 09-03-2018, 12:22 PM
Replies: 31
Views: 1,262
Posted By Radio Fox
Re: "overvolting" transmitters for more power

I agree about the 50 Ohm load instead of the antenna, but 40v P-P is the correct voltage for 4W.

40v P-P = 20v peak = 14.14v RMS. 14.14/50 = 4W.
Forum: General Electronics Technical Discussion 09-03-2018, 12:14 PM
Replies: 31
Views: 1,262
Posted By Radio Fox
Re: "overvolting" transmitters for more power

The maths involved in explaining how you can generate a peak to peak voltage greater than the supply voltage can be quite complicated if you want to go right back to basics.

When I built my...
Forum: General Electronics Technical Discussion 09-02-2018, 05:38 AM
Replies: 31
Views: 1,262
Posted By Radio Fox
Re: "overvolting" transmitters for more power

In my Medium Wave pirate days, I used the same method to check the output of my transmitters.

Using a 50W dummy load, I would tap the voltage across it using my Tektronix 2445B scope & use...
Forum: General Capacitor Questions & Issues 09-02-2018, 04:25 AM
Replies: 21
Views: 1,223
Posted By Radio Fox
Re: Help for Newbie on measuring capacitance

...and an expensive Fluke meter reads them even higher.
Forum: General Capacitor Questions & Issues 08-26-2018, 04:54 AM
Replies: 21
Views: 1,223
Posted By Radio Fox
Re: Help for Newbie on measuring capacitance

All ESR meters give a reading in Ohms (Equivalent Series Resistance). Some also give a capacitance reading.
Forum: General Capacitor Questions & Issues 05-22-2018, 09:14 AM
Replies: 5
Views: 705
Posted By Radio Fox
Re: Ebay seller

He's back.

https://www.ebay.co.uk/sch/h.m.comp/m.html?_nkw=&_armrs=1&_ipg=&_from=
Forum: General Capacitor Questions & Issues 05-15-2018, 04:12 AM
Replies: 5
Views: 705
Posted By Radio Fox
Re: Ebay seller

I have used h.m.comp many times in the past. Always super fast dispatching the parts. Along with semtech1, these were the 2 sellers I would order my Panasonic low ESR caps from.

Hope it's only a...
Forum: Custom Tweaks, Modifications, and Revisions 04-21-2018, 07:38 AM
Replies: 21
Views: 1,542
Posted By Radio Fox
Re: My basic project - needs simplified - Digital TTL circuit maybe

We tend to forget about old fashioned disrete components these days. If we want to latch a bulb, then why not use a latching component (SCR) to do so!

It will only work for incandescent bulbs...
Forum: Custom Tweaks, Modifications, and Revisions 04-20-2018, 11:19 AM
Replies: 21
Views: 1,542
Posted By Radio Fox
Re: My basic project - needs simplified - Digital TTL circuit maybe

Couldn't stand those silly button symbols any longer.

Used DipTrace's component editor to design some better looking ones.
Forum: Custom Tweaks, Modifications, and Revisions 04-19-2018, 04:36 PM
Replies: 21
Views: 1,542
Posted By Radio Fox
Re: My basic project - needs simplified - Digital TTL circuit maybe

My original idea to reset the circuit was to simply have a momentary push to break switch in the 5v supply (Quiz_buttons2.pdf), but that always seems like a bit of a bodge for some reason.

Putting...
Forum: Custom Tweaks, Modifications, and Revisions 04-19-2018, 08:02 AM
Replies: 21
Views: 1,542
Posted By Radio Fox
Re: My basic project - needs simplified - Digital TTL circuit maybe

Sounds like an ideal use of an octal latch like the 74LS373.

Input pins D0-D5 are held high by R1-R6 which is reflected on output pins 0-5 keeping LEDs D7-D12 off.

Suppose, for example, S4 is...
Forum: General Capacitor Questions & Issues 04-15-2018, 09:21 AM
Replies: 14
Views: 5,696
Posted By Radio Fox
Re: What about all these SMD capacitors with no marking?

Interesting article.

I never realised how drastically their capacitance could plummet with just a few volts of bias! :eek:
Forum: General Capacitor Questions & Issues 04-15-2018, 08:40 AM
Replies: 14
Views: 5,696
Posted By Radio Fox
Re: What about all these SMD capacitors with no marking?

The size of the SMD components is determined by the series number (0402, 1206, 2010 etc.) which indicates the package dimensions, so the value cannot be determined by size & shape alone, as there...
Forum: General Electronics Technical Discussion 11-11-2017, 04:35 AM
Replies: 2
Views: 383
Posted By Radio Fox
Re: component identification help

It's a Reed switch. Operated when a magnetic field comes near.
Forum: General Electronics Technical Discussion 11-11-2017, 04:13 AM
Replies: 204
Views: 5,802
Posted By Radio Fox
Re: 555 countdown timer design question

Was that a design consideration? I'm loosing track. LOL.

How about an AND gate that keeps the relay transistor turned on if there is still a high on the 4027 clock pin? The other input to the AND...
Forum: General Electronics Technical Discussion 11-08-2017, 08:04 AM
Replies: 204
Views: 5,802
Posted By Radio Fox
Re: 555 countdown timer design question

Yep, that's the chip. Also known as CD4027 & MC14027.

My initial thoughts were to incorporate the flip flop into the 555 circuit, but eccerr0r's idea is much neater. If your going to use a flip...
Forum: General Electronics Technical Discussion 11-08-2017, 07:34 AM
Replies: 204
Views: 5,802
Posted By Radio Fox
Re: 555 countdown timer design question

Nice. As well as the toggle function with a single push switch, it does the timing as well, with just half a chip.

Along similar lines, you could do away with the shorting transistor & use the Q...
Forum: General Electronics Technical Discussion 11-05-2017, 03:34 PM
Replies: 204
Views: 5,802
Posted By Radio Fox
Re: 555 countdown timer design question

As stj says, you need to look for a flip flop or sequential switching bistable circuit to integrate into the design, so that when the trig pin is taken low, the reset pin is taken high & vice versa....
Forum: General Electronics Technical Discussion 11-05-2017, 03:17 PM
Replies: 204
Views: 5,802
Posted By Radio Fox
Re: 555 countdown timer design question

There's no reason why keeping the button pressed should have any detrimental effects. It will just keep the output high until the switch is released.

100uF 16V (or higher voltage) tantalums are...
Forum: General Electronics Technical Discussion 11-04-2017, 08:11 PM
Replies: 204
Views: 5,802
Posted By Radio Fox
Re: 555 countdown timer design question

I suppose it depends on the application as to how accurate you want the timer to be. I assume in Dannyx's case where it's needed to keep a light on for around a minute, precision timing isn't...
Forum: General Electronics Technical Discussion 11-04-2017, 07:40 PM
Replies: 204
Views: 5,802
Posted By Radio Fox
Re: 555 countdown timer design question

That's right. If you ground the trigger pin again, before the timing cycle has finished, it will have no effect. e.g. if you press the button momentarily 30 seconds into your 1 minute timer, it will...
Showing results 1 to 25 of 240

 
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