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Re: Further to my query of a flashing LED circuit not working

 
Edited

On Wed, Nov 13, 2024 at 01:26 AM, Ian Bell wrote:
Re R3 resistor. The LED is a 5mm red one, and the input voltage is 5-12VDC, but I will be running it at 9VDC. What would you recommend if I was to replace the 270K resistor?
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I do not recommend any value.? It is for you to decide.? Read on.
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The size of the package it is in makes little if any difference.? The color makes some difference, but the key, most important things are:
  1. What is the range of rated currents for your LED?
  2. How bright do you want it to be?
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LED brightness is affected by current.? You can generally "dial down" the brightness by using less than the "rated" or maximum current for that LED.? But you should not "dial up" the current by using more.? (I have seen what happens.? If I remember correctly, the LED's cover was launched about 10 feet across the room.)
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First, look at the datasheet for the LED.? Determine what are the recommended and maximum currents.
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Then, ask yourself if you want it to have full brightness, or if you wish it to be only a soft glow and not blind you while you are trying to sleep.? If the latter, I think you will need to use trial-and-error to find what is a good current for your application.
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At 270 K ohms, the current is 33 uA or less, which strikes me as rather low for most LEDs, and it is probably more like 25 uA if you subtract a few volts for the LED and (small) voltage drop in the 555.
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Andy
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Re: Chasing the "mythical" NE-1 neon bulb

 

wn4isx <wn4isx@...> wrote:

AC/DC radios most often had one side of the AC mains wired to the
chassis. Which gave you a 50/50 chance of a hot chassis given
non-polarized 2 conductor power plugs. Later units "isolated" the
chassis with a capacitor, still deadly.
And to make matters worse, some sets used a single-pole mains switch
connected to the chassis. So, plud it in one way, it's live when it's
on, the other way it's live when it's off!

If I come across one of those, it's changed pronto!

--
rgds
LAurence
<><

The older I get, the smarter I was.
~~~ Random (signature) 1.6.1
Re: files

 

cheers andy,i thought thats what i would have to do,its no problem as i fixed my eagle issue that was giving me grief,thanks all+73
Re: Further to my query of a flashing LED circuit not working

 

Thank you for your reply.
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Re R3 resistor. The LED is a 5mm red one, and the input voltage is 5-12VDC, but I will be running it at 9VDC. What would you recommend if I was to replace the 270K resistor?
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Ian
Re: Further to my query of a flashing LED circuit not working

 

On Tue, Nov 12, 2024 at 09:07 PM, Ian Bell wrote:
Can I use an electrolytic 63V, 1uF or another type such as a Tantalum or a 100v Non-polarised type.?
I would think so - yes,? yes, and yes.
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FYI, a Tantalum capacitor is an electrolytic.? The two main kinds of electrolytic caps are Aluminum and Tantalum.
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Electrolytics may not be the world's greatest capacitor type, but should be fine in this circuit.? But be aware that most electrolytic caps have rather wide tolerances on the capacitance value, so the flash rate might differ from ideal by a little.
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The 270 K value for R3 seems awfully large.? But that value depends on the LED and the battery voltage.
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Andy
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Re: any kicad 8 experts here?.

 

Paul?
I agree that it is not the best, but found it quite easy by rotating the parts to approximate the schematic then just link them using the rats nest lines l linked them all up.
Tony
File /Flashing LED circuit_2_PCB layout.jpg uploaded #file-notice

Group Notification
 

The following items have been added to the Files area of the [email protected] group.

By: Ian Bell <genealogyinfo@...>

Description:
Further to my query of a flashing LED circuit not working. (PCB solder side layout)
Re: Further to my query of a flashing LED circuit not working

 

I am also attaching to the files, a scan of the PCB solder side. Hope it is clear enough. The capacitor is located between the resistors R1 & R3.
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Ian
File Notifications #file-notice

Group Notification
 

Ian Bell <genealogyinfo@...> added folder /Further to my query of a flashing LED circuit not working

Description:
Circuit for "Further to my query of a flashing LED circuit not working"

The following items have been added to the Files area of the [email protected] group.

By: Ian Bell <genealogyinfo@...>

Description:
Further to my query of a flashing LED circuit not working
Further to my query of a flashing LED circuit not working

 

Hi there, again,
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Further to my query of a flashing LED circuit not working. From all the comments I've had, it seems as though it is a "dud" circuit, consequently I have gone to the "Plan B" circuit which I discovered when I was searching for a simple flashing circuit. This uses an NE555 timer IC. I will attach the circuit shortly in the files section. To summarise it has the 555 timer, 3 resistors - 100K ohms, 270K ohms, & 470K ohms, 1 capacitor - 1uF, and of course the Red 5mm LED. The circuit uses a 5-12VDC supply. Can I use an electrolytic 63V, 1uF or another type such as a Tantalum or a 100v Non-polarised type.?
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FWIW, I'm putting a navigation type flashing light on top of a building I'm making for my model RR layout.
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Thanks,
?
Ian
Re: Chasing the "mythical" NE-1 neon bulb

 

On Tue, Nov 12, 2024 at 02:30 PM, wn4isx wrote:
I'm assuming both 55V-55V were isolated from ground.
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If they were, I think there would be no point to calling it 55V-55V, or 55 volts on each line.? The implication is that each line's voltage is measured against some other reference - presumably, ground.
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But I could be wrong.
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Andy
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Re: current limited npn not allowing NPN to open

 

By the way, the 1K resistor R1 does nothing useful.? Because you drove the Base with a current source, the resistor R1 does not change that in any way.
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Andy
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Re: current limited npn not allowing NPN to open

 

On Tue, Nov 12, 2024 at 04:04 PM, john23 wrote:
Why in saturation Ic/Ib is ver very small?
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Because you can't get any more current than that.? When it is in saturation, it can't turn on any harder and that is all the collector current that is possible.? It is basically limited by the rest of the circuit around the transistor.
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In your case, you subjected the NPN to a base current from 1 mA to 20 mA.? If the transistor's Beta was 200, then the collector current would have to be between 200 mA and 4 Amps.? It is physically impossible.? The absolute maximum collector current in your circuit would be 5/(1K+100) = 4.5 mA, which is MUCH smaller than either 200 mA or 4000 mA.
?
In order to get Ic = 4000 mA, the collector voltage would have to be pulled down to -395 volts!? But there is no negative supply voltage in your circuit, so that is just plain impossible.? Transistors can not generate voltages from nothing.
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Andy
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Re: files

 

Hi all,is it possible to attatch a file here?
I just checked the settings, and it says attached files are automatically Stripped (removed from messages) by the servers.? So, don't try.
?
... and need to upload the schematic+ board files but cant see how i can do that, Is it possible?
The best way to do that is by uploading them to Files.? It is one of the choices in the menu (on the left if using a PC).? Navigate to Files, then look for the "New/Upload" button near the top.
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Andy
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Re: any kicad 8 experts here?.

 

¿ªÔÆÌåÓý

You can use FreeRoute with KiCad.?



On Nov 12, 2024, at 4:44?PM, Paul M3VUV via groups.io <nanovnauser@...> wrote:

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i gave up on kicad as it has no autorouter,i am trying eagle instead now.

Re: Chasing the "mythical" NE-1 neon bulb was something wrong

 

I recall my mother complaining that she felt a "tingle" when touching the stainless steel edge on her Formica counter top while opening the refrigerator. I was probably 10 at the time but I knew enough to run a ground from the BX cable to the counter edge. It was probably some leakage in the fridge compressor but it took a while for her to convince my father there was something wrong. This was in the early 50's so there were no polarized plugs.

Dan Kahn
On Tuesday, November 12, 2024 at 12:07:25 PM EST, wn4isx via groups.io <wn4isx@...> wrote:


I guess it's time to bring up "The All American Five" and AC/DC operation.
Parts of Detroit were 110V DC up until sometime in the 1960s. An aunt lived there and told me of the woes of getting a TV that worked.
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AC/DC radios most often had one side of the AC mains wired to the chassis. Which gave you a 50/50 chance of a hot chassis given non-polarized 2 conductor power plugs. Later units "isolated" the chassis with a capacitor, still deadly.
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The outer case and knobs were designed to prevent contact with the chassis.
My younger sister pulled Mom's radio off the table, shattered the case. I was told the throw the radio away, saved it, plugged in and it worked. I was 7 and touched the case. Our garage had a dirt floor and I was barefooted and got the urine knocked out of me. My father demonstrated the danger with a light bulb. That lesson stayed with me.
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So if you are restoring an All American Five (no idea why anyone would the performance was amazingly mediocre) be aware the chassis might be hot.
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Oh, the insulation in pre ?1970 Singer sewing machines was marginal and the case could easily be hot.
My older sister was shocked on Mom's Singer.
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And, lights are supposed the have the shell wired to neutral. Even with polarized 2 conductor mains connectors, do not trust the wiring!!!! Been bit once really good because I assumed "surely they wired it
properly at the factory." Nope. shell was hot, switch was in the neutral.
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Trust but verify applies to electronics as well as international weapons treaties.
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Re: any kicad 8 experts here?.

 

i gave up on kicad as it has no autorouter,i am trying eagle instead now.

files

 

Hi all,is it possible to attatch a file here?,i am struggling trying to make a pcb for toner transfer using eagle and need to upload the schematic+ board files but cant see how i can do that, Is it possible?.thanks all.

Re: current limited npn not allowing NPN to open

 

I think you meant Collector-Emitter saturation voltage is around 0.2V, correct?? The Base-Emitter voltage is typically 0.6V.

Re: current limited npn not allowing NPN to open

 

Hello,the purpose of biasing NPN threw current source is to calculate the limiting resistor needed for supplying the base of the NPN.
Why in saturation Ic/Ib is ver very small?
Thanks.

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