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

 

On Wed, Nov 13, 2024 at 07:28 PM, wn4isx wrote:
I've not checked but are modern US cars not available with manual transmissions?
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Don't take my word on it - but I read that stick shifts ceased to be an option on any US-sold cars a few years ago, including imports.? Bummer.
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Andy
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Re: Two other ways to flash LEDs

 

On Wed, Nov 13, 2024 at 09:30 PM, miktrain wrote:
... using 3 5K resistors, hence the name 555 ...
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That is an interesting bit of trivia.? But I wonder if there is any truth to it or if it is just folklore that came along years after-the-fact.
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As I recall, the 555 (SE555/NE555) was from Signetics which already was using ICs with numbers in the 500's.? In analog/audio, some of the others I recall from that period were the 531 (high slew rate op-amp), 540 (output power driver), 565 (PLL), 566 (VCO), and 567 (PLL tone decoder).? So the 555 kind of slipped in there by happy coincidence, I suspect.
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Andy
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Re: Further to my query of a flashing LED circuit not working

 

My 1939 Plymouth Pickup truck is three on the floor with double clutching required. No Synchro trans.

Dan Kahn
On Wednesday, November 13, 2024 at 06:54:49 PM EST, Andy via groups.io <ai.egrps@...> wrote:


But who can drive a standard transmission?
I wish we Americans could still do that - that it were still possible to get cars equipped with a standard shift.
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Andy
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Re: Two other ways to flash LEDs

 

555 timers also are not subject to voltage. Anything from 5 to 16 volts will give exactly the same timing because they work on deviding the supply by 3 using 3 5K resistors, hence the name 555 and switch at 1/3 and 2/3
Re: Further to my query of a flashing LED circuit not working

 

Ian,
The LED will not light with that 270k, change it to about 1K maybe a bit more if you want it dim.
Tony
Re: Chasing the "mythical" NE-1 neon bulb

 

¿ªÔÆÌåÓý

I grew up in Detroit (Brightmoor neighbourhood), but our service was 60Hz. I do remember touching the little B/W teevee in the kitchen while washing dishes (or something) and getting a serious tingle. Survived and forever after allowed only one hand loose in the vicinity of an electrical device.

Donald.

On 11/12/24 12:07, wn4isx via groups.io 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: Further to my query of a flashing LED circuit not working

 

But who can drive a standard transmission?
I wish we Americans could still do that - that it were still possible to get cars equipped with a standard shift.
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Andy
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Re: Further to my query of a flashing LED circuit not working

 
Edited

On Wed, Nov 13, 2024 at 06:11 PM, wn4isx wrote:

... But, who is going to steal a 2001 Toyota Echo or 2002 Volvo S60?

Some of those older year models are quite valuable today.? Until not long ago we had a ~2003 Toyota.? The service shop told us never to sell it.? Owners were not selling them because they knew how good they were.
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I don't pretend to know anything about different car models.
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Andy
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Re: Further to my query of a flashing LED circuit not working

 

On Wed, Nov 13, 2024 at 05:22 PM, Gooey wrote:
What is a FLASHING LED?? I thought it was an LED that blinked regularly as long as power was applied to it.
Correct, sort of.
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But it is not limited to LEDs designed to flash all by themselves with no external circuitry.? A "flashing LED circuit" includes a circuit designed to flash a LED.? This topic had been about a circuit that flashes an ordinary LED.? The LED flashes, but not without help of the circuit that makes it flash.
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I'm sure you can also buy LEDs that flash themselves.? All that means is that they included the other circuitry on the die (or inside the package) with the LED itself.
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Andy
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Re: current limited npn not allowing NPN to open

 

On Wed, Nov 13, 2024 at 02:53 PM, john23 wrote:
2. suppose I have a 3V voltage source instead of? the current source.
I want to stay in linear state where Ib=45uA Ic=9mA as shown in the plot below.
How do i calculate the needed limiting resistor if I replace the curent source with 3V voltage source?
Here is one approach to answering that question:
  1. Ic = 9 mA suggests that Ie = approx. -9 mA as long as Beta is large.
  2. Ve = approx. 9 mA * 100 = 0.9 V.
  3. Vb = approx. 0.9 + 0.7 = 1.6 V.
  4. Now you know you need 3.0 - 1.6 = 1.4 V drop across R1.
  5. When Ib = 45 uA, then R1 = 1.4 / 45u = 31 Kohms.
    • But that is with Beta = 200, but Beta could be between 100 and 500 at least (*).
    • At Beta = 100, Ib = 90 uA, so R1 = 1.4 / 90u = 15.5 Kohms.
    • At Beta = 500, Ib = 18 uA, so R1 = 1.4 / 18u = 77.8 Kohms.
    • To keep Ic ¡Ü 9 mA, use R1 = 77.8 Kohms.
  6. Check for saturation:? Ic = 9 mA drops 0.9 V across R3, so Vc = 4.1 V, making Vce = 3.8 V and the transistor is not saturated, but only if Ic is not allowed to exceed 9 mA.
  7. By choosing R1 at maximum Beta, we tried to keep Ic ¡Ü 9 mA, so we are pretty sure it will not saturate over the range of Beta values.
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(*) But there are two more things to consider, and they can affect the calculations:
  1. Temperature.? Beta can vary over more than 3:1 range due to temperature alone, on top of the part-to=part variation.? What if Beta approaches 1000?? Vbe also decreases with increasing temperature.
  2. Counterfeit parts.? Chances are fair that you won't get a real 2N2222 even if you buy one with that marked on it.? Many transistors today are from China and many Chinese parts are counterfeit and some of them have quite different characteristics than what they should be.? This is true even for semiconductors marked with American or Japanese or Taiwanese or Dutch manufacturer names on them.
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Andy
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Re: Further to my query of a flashing LED circuit not working

 

What is a FLASHING LED?? I thought it was an LED that blinked regularly as long as power was applied to it.

Based upon my (mis?) understanding, all one needed was the DC power (and, possibly a resistor) to make a flashing light.

I ask because I have been tinkering around with the idea of making a few lithium cell powered devices I could place about the property so that 'intruders' my assume there was some sort of security monitoring device about. I was hoping to employ some sort of component that turned it on after dark since, in broad daylight, it would be unlikely to fool most folks.


--
G.T.
Re: current limited npn not allowing NPN to open

 
Edited

On Wed, Nov 13, 2024 at 02:53 PM, john23 wrote:
Hello Andy, I biased my NPN to design the limiting resistor.
What "limiting resistor" are you talking about?
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As I explained already, resistor R1 does not limit anything in your circuit.? The current into the Base exactly equals the current from I1.? Adding that resistor R1 changes nothing.? (Well, it changes the voltage at the top of I1, but it does not change anything at the NPN BJT.? The current source I1 drives its specified current exactly, regardless of the voltage.)
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by your previus advice my maximal current should be 1000*(5/200)=25mA which is exactly the saturation current i got in the plot below.
I'm sorry, but I do not folllow.? Where is this "maximal current"?? Through what?? Where did you get that formula?
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If "200" represents the NPN transistor's Beta, note that that number is very approximate.? In fact, the 2N2222 in the simulation had a Beta greater than 200 when I simulated it.
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In real circuits with real transistors, the Beta can vary over a very large range.? The datasheet (referred to earlier in this topic) shows a range of 30 to more than 325, and the range at a single operating point?can be at least as much as 325/75 which is a ratio of 4.3:1.? In other words, one 2N2222 might have a Beta that is 4.3 times another 2N2222, under the same conditions.? Note that some of the numbers on the datasheet are omitted.? For example, there is no maximum Beta at Ic=10 mA and Vce=10 V.? It might be as high as 1000 or more.? It probably won't be, but where do you put the upper limit?? There is none.
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... 25mA which is exactly the saturation current i got in the plot below.
That is not what you showed in your plot.? It does not reach 25 mA.
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I have made a simulation shown below by your advice where I lowered the current going into the base.?
Three questions:
1.In the plot I saw the when the collector? current is saturated? Vce is very low .
Why the Vce is very low in this state?
Because that is what it means to be "saturated".
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Get a book about bipolar transistors, and read about them.? You need to learn how transistors work, before you can use them.
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When the base current increases, the collector current TENDS to increase also, while the transistor turns ON more.? But when Ic increases, the voltage drop across R3 makes the collector voltage fall.? Eventually it reaches the point where Vce is nearly zero.? When that happens, the transistor can not turn ON any more.? It can not pull the collector voltage any lower.? If it could, it would make Vce negative, which is impossible.
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When Vce becomes very low and it can't go any lower, that means the transistor is saturated and can not make its Ic larger than it is.
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2. suppose I have a 3V voltage source instead of? the current source.
I want to stay in linear state where Ib=45uA Ic=9mA as shown in the plot below.
How do i calculate the needed limiting resistor if I replace the curent source with 3V voltage source?
What is the "limiting resistor"?? Do you mean R1?? R2?? R3?
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Is there something you are trying to accomplish with this circuit, or are you just fooling around to learn about circuits with transistors?? It feels like it is pointless trying to answer a question like that, when there is no particular reason to hand-hold someone through all the calculations that they are not willing to do, or incapable of doing.
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Andy
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Re: current limited npn not allowing NPN to open

 

Hello Andy, I biased my NPN to design the limiting resistor.by your previus advice my maximal current should be 1000*(5/200)=25mA which is exactly the saturation current i got in the plot below.
I have made a simulation shown below by your advice where I lowered the current going into the base.?
Three questions:
1.In the plot I saw the when the collector? current is saturated? Vce is very low .
Why the Vce is very low in this state?
2. suppose I have a 3V voltage source instead of? the current source.
I want to stay in linear state where Ib=45uA Ic=9mA as shown in the plot below.
How do i calculate the needed limiting resistor if I replace the curent source with 3V voltage source?
Thanks.
?
Re: Chasing the "mythical" NE-1 neon bulb

 

On Tuesday 12 November 2024 02:30:41 pm wn4isx via groups.io wrote:
Not that I will ever be on any US Navy ship, where the 55V-55V outlets standard NEMA 5-15R, what you have in any US residence build since 1970, a connector with a ground connection?
I'm assuming both 55V-55V were isolated from ground.
Every outlet in this 100 year old house has been replaced with one that has a ground connection. Unfortunately my handy outlet tester shows me that a fair number of them don't have any connection to that ground pin...

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Re: Chasing the "mythical" NE-1 neon bulb

 

On Tuesday 12 November 2024 12:07:22 pm wn4isx via groups.io 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.
The same was true of parts of Manhattan, lower east side as far as I know. I was in this apartment once and was warned not to plug in this little radio that I had because it'd burn out the transformer in it (no batteries at the time).

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.
I've always thought that those polarized plugs were a PITA.

(...)
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.
I have no particular desire to mess with those radios, must be a nostalgia thing or something I'd guess. Another fun thing about those is that the power switch was wired in the side of the line that connected to the chassis. OTOH, I have this 1941 RCA console radio...

It uses a 5Y3 for a rectifier. Somebody had stuck a 5U4 in there, which I guess could've worked but drawing 3A instead of 2A for the filamet of that tube put unnecessary stress on the power transformer. And somewhere along the line somebody had replaced most of the line cord with the cord from a TV, just stuck the wires into those holes, strands sticking out and not terribly safe. And the guy I got it from claimed to be an electrician by trade.

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Re: current limited npn not allowing NPN to open

 

On Wed, Nov 13, 2024 at 10:08 AM, wn4isx wrote:
On Tue, Nov 12, 2024 at 08:45 PM, Andy wrote:
In order to get Ic = 4000 mA, the collector voltage would have to be pulled down to -395 volts!
Color me confused,
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Look at the circuit external to the NPN.
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In order to have 4 Amps of current into the NPN's collector pin, its collector voltage would need to be at +5volts - (4amps * 100ohms) = -395volts.? That is the only way to get 4000 mA through the resistor and into the collector.? That only works if the other stuff, connected to the NPN's base and emitter pins, have some different voltages on them.
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If you managed to do that, and if nothing goes up in smoke, then yes, you could have Ic = 4000 mA.? And if the 2N2222's Beta is still around 200 at that level - which it probably is not - and if the 2N2222 is even capable of sinking 4000 mA - which its datasheet says it is not - then you would see Ic/Ib where you thought it might be.? But there are rather significant IF's in that situation and it simply would not work even under those conditions.? Indeed the hfe drops significantly by the time you reach only 500 mA.? By 4000 mA it has probably disappeared.
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Putting it another way, the emitter and base voltages would need to be somewhere around -400 V or more negative.? And then you still get V(c) > V(e) and V(c) > V(b), just like normal NPN operation.
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All normal NPN circuits I've seen have the collector tied to V+ either through a resistor, inductor or transistor, or directly for an emitter follower.
Then I think you have not seen that many NPN circuits.? (No, I'm only joking.? I am sure you have seen many others, which have voltages all over the place.? Everything is relative.)
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Andy
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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
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