electronics question?

[jimbo84]

I'm tearing my hair out, I want to make a blue alternate blinking led circuit.

This is the 5th one I've tried on a bread board and all I ever get is constantly on LEDs

Is this circuit flawed and will never work or is it me doing something wrong?

I used to manage stuff like this really easily but now my brain just fogs up.

I've also tried putting the 1k resistors in series with the LEDs.

Also tried upping the voltage slightly and once at 4v my bench supply is switching to constant current mode and not increasing voltage, I don't know why it's doing this?



This is the current mess on the breadboard.

 

[julianthegypsy]

I can't remember how, but I've made blinking leds that could go from a slow blinking to fully on, like a dimmer switch, using an arguing board. It had to be reprogrammed to change it but I could have got round that by adding a potentiometer I think.

 

[ajlelectronics]

It is one of the features of that circuit, it is possible to deal with it by adding a couple of diodes. However you haven't shown the capacitor polarity. You are risking the LEDs too like that, as they need to be limited to about 20mA forward current.

Actually, try incandescent bulbs without the 1K rather than LEDs or if you have none, just monitor the Voltage at the collectors with the LEDs disconnected.

Do you need that actual circuit for experience, or is the function more important?

 

[Robotstar5]

The good old astable multivibrator, try this one.

 

[ajlelectronics]

The breadboard looks wrong too. Column 46 carries the wire, yet column 47 has the capacitor leg.

 

[Seadog]

Column 46 carries the wire, yet column 47 has the capacitor leg.

47 & 48

 

[ajlelectronics]

47 & 48

Ecsaktlee!

 

[charliecambs]

Years ago I worked for a company ( Newmarket Transistors "NKT".
we made UKs early germanium transistors then as part of PYE/PHILIPS used silicon transistors as unpackaged chips in modules( this in the 70's)
We used to pick two adjacent chips from the manufactured wafer containing many thousands and assemble into a package to make the early versions of operational/ differential amplifiers.

The relevance to the multivibrator is that they were often so well matched that the circuit wouldn't start to oscillate!

 

[Seadog]

I've some 'NKT' transistors somewhere.

 

[jimbo84]

I finally managed to make a circuit that worked with a 555 chip.

This one


My 2 year old loves fire engines at the moment and has a toy box one from Aldi so I wanted to make him a blue flashing light to go with it. One with a big switch on it that he could turn on and off. This was the reason for attempting to make the circuit.

Once I'd got it working on the breadboard I soldered it to a DIY solderboard.


Put a couple of lenses into an outside lightswitch


Mounted in the DIY circuit board


Soldered in a 9v battery (no connector leads for the battery) No pics of that bit.
Together


It flashes alternate lights when switched on.

 

[jimbo84]

It is one of the features of that circuit, it is possible to deal with it by adding a couple of diodes. However you haven't shown the capacitor polarity. You are risking the LEDs too like that, as they need to be limited to about 20mA forward current.

Actually, try incandescent bulbs without the 1K rather than LEDs or if you have none, just monitor the Voltage at the collectors with the LEDs disconnected.

Do you need that actual circuit for experience, or is the function more important?

It was more for the function than for doing it a specific way. Everyone I tried wouldn't work. The 555 one above was about 6th time lucky!

 

[jimbo84]

The good old astable multivibrator, try this one.
View attachment 425594

I'd spotted that one or one very similar but only had 1 10uf cap in my stock of bits. Thanks though.

 

[Chippie]

I'd spotted that one or one very similar but only had 1 10uf cap in my stock of bits. Thanks though.

The caps don’t have to be the same value, changing the value will mean a different on time( or off ) compared to the other led…if you scoped the output, the pulse width would be asymmetric..

 

[ajlelectronics]

The caps don’t have to be the same value, changing the value will mean a different on time( or off ) compared to the other led…if you scoped the output, the pulse width would be asymmetric..

Also you can compensate by increasing the resistance.

 

[Smallfry]

You can buy high intensity flashing LEDs that need no other components though ?

Not that I know anything about electronics anyway !

 

[Hotstuff]

Brilliant…..I bet your lad will have a great time with that.
Just one question……where’s the siren

 

[jimbo84]

You can buy high intensity flashing LEDs that need no other components though ?

Not that I know anything about electronics anyway !

Yeah you can get ones that already flash but that would be far too easy

I'd wanted to make it out of stuff I had on the day, rather than waiting for bits and then me never getting round to it which is usually how these things go for me.

 

[Dev]

Treat yourself to one of these https://thepihut.com/products/maker-advent-calendar-let-it-glow-inc-raspberry-pi-pico-h

edit: if you do want neenaws I got this for my kids toylander- no coding required