This seems like a simple thing to find, but I've failed thus far.
We have quite a long driveway so I want to build a gizzmo that sounds a beeper in the house for a period (30-60 seconds) when the gate is opened
and then flashes a light until the gate is closed. The light needs to be bright and to look OK on the hall wall, ideally with enough space inside
to contain a bit of circuitry and a piezo sounder. The gate switch and cabling are already in place. I'd prefer to power the thing from one of
the many spare USB chargers that are in the drawers, hence the 5V spec.
The electronics are trivial but I can't find a suitable light that I can flash (with a 555 astable). Any suggestions?
This seems like a simple thing to find, but I've failed thus far.
We have quite a long driveway so I want to build a gizzmo that sounds a beeper in the house for a period (30-60 seconds) when the gate is opened
and then flashes a light until the gate is closed. The light needs to be bright and to look OK on the hall wall, ideally with enough space inside
to contain a bit of circuitry and a piezo sounder. The gate switch and cabling are already in place. I'd prefer to power the thing from one of
the many spare USB chargers that are in the drawers, hence the 5V spec.
The electronics are trivial but I can't find a suitable light that I can flash (with a 555 astable). Any suggestions?
This seems like a simple thing to find, but I've failed thus far.wall, ideally with enough space inside to contain a bit of circuitry and a piezo sounder. The gate switch and cabling are already in place. I'd prefer to power the thing from one of the many spare USB chargers that are in the drawers, hence the 5V spec.
We have quite a long driveway so I want to build a gizzmo that sounds a beeper in the house for a period (30-60 seconds) when the gate is opened and then flashes a light until the gate is closed. The light needs to be bright and to look OK on the hall
On Mon, 5/19/2025 12:54 PM, No mail wrote:wall, ideally with enough space inside to contain a bit of circuitry and a piezo sounder. The gate switch and cabling are already in place. I'd prefer to power the thing from one of the many spare USB chargers that are in the drawers, hence the 5V spec.
This seems like a simple thing to find, but I've failed thus far.
We have quite a long driveway so I want to build a gizzmo that sounds a beeper in the house for a period (30-60 seconds) when the gate is opened and then flashes a light until the gate is closed. The light needs to be bright and to look OK on the hall
LEDs have a forward voltage drop Vf. The LED will
not light, unless at least Vf is applied to the legs.
A red LED is 1.6V perhaps.
A white LED (which is a blue LED plus a phosphor) is 2.5V (at 10mA).
For the high current LEDs (350mA or 700mA) the voltage
is closer to 3.5V on those.
The 5V supply has sufficient voltage, to run one LED.
You can see in the example, this budding designer is able to
run some amount of loading with his ideas. You can make arrays of LEDs,
equip each LED with a resistor, and drive a decent power source into
the thing. I have two 4x12 arrays running at 10mA per LED, for 480mA total current (each one using about half a 5V 1A adapter).
https://www.eleccircuit.com/ic-555-led-flasher/
In the one circuit, he uses an NPN for high side drive.
and a PNP for a low side drive. All based on the voltage
seen on the Output pin of the 555. The 555 has limited current
source and sink capability -- the external transistors are
buffers to drive higher loads.
The second circuit, with the transistors arranged as a Darlington
on the output, the signal driving the Darlington tree is
coming off the timing capacitor node. Maybe that is why there
are three transistors in the Darlington structure, to lift
the threshold voltage to turn on the incandescent light he happens
to be using as a load.
You can place a few components, after the NE555, to drive
larger loads. You have to know a small amount about electronics,
the biasing of transistors, to do some of those tricks
(without smoking something and ruining it).
*******
You can use LEDs which are mounted on an alumina substrate for home projects. This takes care of the tricky detail of soldering things directly to the LED. Ordinary soldering can be done to the pads on the alumina substrate.
https://www.kge.ca/en/product/lighting/22022-star-base-led-20mm-x-20-mm-3w-aluminium-pcb.html
https://www.kge.ca/DATA/PRODUIT/22022~v~star-base-led-20mm-x-20-mm-3w-aluminium-pcb.pdf
3.8V @ 750mA WW = warm white, thicker phosphor, 210 lumens
W = blue white, thinner phosphor, 230 lumens
At that power level, the star substrate gets hot, and should be fastened
to a piece of scrap metal for cooling purposes.
Using the smaller LEDs and making an array of LEDs, is a bit better with regard to cooling issues. But it also takes a lot of resistors (which are needed to control and limit current flow). Some suppliers of electronic compoents, charge 20x as much for resistors as other companies, so you
don't buy your bulk leaded resistors from boutique stores that charge too much.
$0.05 per resistor, $0.20 per small T1 3/4 LED, is enough expense.
Super-high-power LEDs are not eye-safe, so use a diffuser to lessen
the risk of eye damage.
The above is not exactly a recipe-grade set of instructions. It's
the beginning of an illustration how to proceed, but many details
must be worked out. Your first circuit will have one tiny LED and
the circuit will not draw a lot of power. You work your way up, scaling
and testing as you go, until you learn how to assemble and drive larger
loads (as a hobbyist).
Paul
On 19/05/2025 17:54, No mail wrote:
This seems like a simple thing to find, but I've failed thus far.
We have quite a long driveway so I want to build a gizzmo that sounds
a beeper in the house for a period (30-60 seconds) when the gate is
opened and then flashes a light until the gate is closed. The light
needs to be bright and to look OK on the hall wall, ideally with
enough space inside to contain a bit of circuitry and a piezo sounder.
The gate switch and cabling are already in place. I'd prefer to power
the thing from one of the many spare USB chargers that are in the
drawers, hence the 5V spec. The electronics are trivial but I can't
find a suitable light that I can flash (with a 555 astable). Any
suggestions?
Is there a signal *in the hall* showing whether the gate is open or not
Is there mains power for the light?
All the light needs to be is a fairly large LED.
You would be surprised how little power is 'noticeable' especially when flashing
I would suggest getting a camper van light like
https://www.amazon.co.uk/Obeaming-Switchable-Campervan-Replacement-Nightlight/dp/B0DHK8H22L/?th=1
And running it off 5V instead of 12V. It wont be noticeably dimmer. You
can mount everything inside
On 19/05/2025 17:54, No mail wrote:
This seems like a simple thing to find, but I've failed thus far.
We have quite a long driveway so I want to build a gizzmo that sounds
a beeper in the house for a period (30-60 seconds) when the gate is
opened and then flashes a light until the gate is closed. The light
needs to be bright and to look OK on the hall wall, ideally with
enough space inside to contain a bit of circuitry and a piezo sounder.
The gate switch and cabling are already in place. I'd prefer to power
the thing from one of the many spare USB chargers that are in the
drawers, hence the 5V spec. The electronics are trivial but I can't
find a suitable light that I can flash (with a 555 astable). Any
suggestions?
You can get LEDs with a built in IC that flash them at approx 1Hz to
2Hz. They operate at around 3.5V and the current is set with a series resistor (from a 5V USB supply). A single LED is extremely bright and noticeable. I recommend selecting the resistor to give MUCH less than
20mA which is specified to give the maximum output light. I also found
a blue LED to be more noticeable.
Random seller on Ebay for 1.5Hz version https://www.ebay.co.uk/itm/284973690845
I've previously used one to warn that the immersion heater has been left
on.
I had a mains to a USB A adapter which I took apart to reveal the very
small module inside (made smaller by un-soldering the USB connector).
This board, and the series resistor, was fitted in a standard plastic
light switch 1 gang back box. A hole was drilled in a 1 gang blanking
plate for the LED.
In my case I just tapped off the immersion heater switch mains supply to
turn the whole system on. In your case you could either switch the mains
or the 5V supply.
You can get LEDs with a built in IC that flash them at approx 1Hz to
2Hz.
Thanks ... but I graduated in Electronic Engineering in the mid 70s.
I was looking for something that looked acceptable to SWMBO when fixed on a wall.
Thanks ... but I graduated in Electronic Engineering in the mid 70s.
I was looking for something that looked acceptable to SWMBO when
fixed on a wall.
Paul wrote:
On Mon, 5/19/2025 12:54 PM, No mail wrote:Thanks ... but I graduated in Electronic Engineering in the mid 70s. I
This seems like a simple thing to find, but I've failed thus far.
We have quite a long driveway so I want to build a gizzmo that sounds
a beeper in the house for a period (30-60 seconds) when the gate is
opened and then flashes a light until the gate is closed. The light
needs to be bright and to look OK on the hall wall, ideally with
enough space inside to contain a bit of circuitry and a piezo
sounder. The gate switch and cabling are already in place. I'd prefer
to power the thing from one of the many spare USB chargers that are
in the drawers, hence the 5V spec. The electronics are trivial but I
can't find a suitable light that I can flash (with a 555 astable).
Any suggestions?
LEDs have a forward voltage drop Vf. The LED will
not light, unless at least Vf is applied to the legs.
A red LED is 1.6V perhaps.
A white LED (which is a blue LED plus a phosphor) is 2.5V (at 10mA).
For the high current LEDs (350mA or 700mA) the voltage
is closer to 3.5V on those.
The 5V supply has sufficient voltage, to run one LED.
You can see in the example, this budding designer is able to
run some amount of loading with his ideas. You can make arrays of LEDs,
equip each LED with a resistor, and drive a decent power source into
the thing. I have two 4x12 arrays running at 10mA per LED, for 480mA
total
current (each one using about half a 5V 1A adapter).
https://www.eleccircuit.com/ic-555-led-flasher/
In the one circuit, he uses an NPN for high side drive.
and a PNP for a low side drive. All based on the voltage
seen on the Output pin of the 555. The 555 has limited current
source and sink capability -- the external transistors are
buffers to drive higher loads.
The second circuit, with the transistors arranged as a Darlington
on the output, the signal driving the Darlington tree is
coming off the timing capacitor node. Maybe that is why there
are three transistors in the Darlington structure, to lift
the threshold voltage to turn on the incandescent light he happens
to be using as a load.
You can place a few components, after the NE555, to drive
larger loads. You have to know a small amount about electronics,
the biasing of transistors, to do some of those tricks
(without smoking something and ruining it).
*******
You can use LEDs which are mounted on an alumina substrate for home
projects.
This takes care of the tricky detail of soldering things directly to
the LED.
Ordinary soldering can be done to the pads on the alumina substrate.
https://www.kge.ca/en/product/lighting/22022-star-base-led-20mm-x-20-
mm-3w-aluminium-pcb.html
https://www.kge.ca/DATA/PRODUIT/22022~v~star-base-led-20mm-x-20-
mm-3w-aluminium-pcb.pdf
3.8V @ 750mA WW = warm white, thicker phosphor, 210 lumens >> W = blue white, thinner phosphor, 230 lumens
At that power level, the star substrate gets hot, and should be fastened
to a piece of scrap metal for cooling purposes.
Using the smaller LEDs and making an array of LEDs, is a bit better with
regard to cooling issues. But it also takes a lot of resistors (which are
needed to control and limit current flow). Some suppliers of electronic
compoents, charge 20x as much for resistors as other companies, so you
don't buy your bulk leaded resistors from boutique stores that charge
too much.
$0.05 per resistor, $0.20 per small T1 3/4 LED, is enough expense.
Super-high-power LEDs are not eye-safe, so use a diffuser to lessen
the risk of eye damage.
The above is not exactly a recipe-grade set of instructions. It's
the beginning of an illustration how to proceed, but many details
must be worked out. Your first circuit will have one tiny LED and
the circuit will not draw a lot of power. You work your way up, scaling
and testing as you go, until you learn how to assemble and drive larger
loads (as a hobbyist).
Paul
was looking for something that looked acceptable to SWMBO when fixed on
a wall.
On 19/05/2025 21:38, No mail wrote:
Paul wrote:
On Mon, 5/19/2025 12:54 PM, No mail wrote:Thanks ... but I graduated in Electronic Engineering in the mid 70s. I
This seems like a simple thing to find, but I've failed thus far.
We have quite a long driveway so I want to build a gizzmo that
sounds a beeper in the house for a period (30-60 seconds) when the
gate is opened and then flashes a light until the gate is closed.
The light needs to be bright and to look OK on the hall wall,
ideally with enough space inside to contain a bit of circuitry and a
piezo sounder. The gate switch and cabling are already in place. I'd
prefer to power the thing from one of the many spare USB chargers
that are in the drawers, hence the 5V spec. The electronics are
trivial but I can't find a suitable light that I can flash (with a
555 astable). Any suggestions?
LEDs have a forward voltage drop Vf. The LED will
not light, unless at least Vf is applied to the legs.
A red LED is 1.6V perhaps.
A white LED (which is a blue LED plus a phosphor) is 2.5V (at 10mA).
For the high current LEDs (350mA or 700mA) the voltage
is closer to 3.5V on those.
The 5V supply has sufficient voltage, to run one LED.
You can see in the example, this budding designer is able to
run some amount of loading with his ideas. You can make arrays of LEDs,
equip each LED with a resistor, and drive a decent power source into
the thing. I have two 4x12 arrays running at 10mA per LED, for 480mA
total
current (each one using about half a 5V 1A adapter).
https://www.eleccircuit.com/ic-555-led-flasher/
In the one circuit, he uses an NPN for high side drive.
and a PNP for a low side drive. All based on the voltage
seen on the Output pin of the 555. The 555 has limited current
source and sink capability -- the external transistors are
buffers to drive higher loads.
The second circuit, with the transistors arranged as a Darlington
on the output, the signal driving the Darlington tree is
coming off the timing capacitor node. Maybe that is why there
are three transistors in the Darlington structure, to lift
the threshold voltage to turn on the incandescent light he happens
to be using as a load.
You can place a few components, after the NE555, to drive
larger loads. You have to know a small amount about electronics,
the biasing of transistors, to do some of those tricks
(without smoking something and ruining it).
*******
You can use LEDs which are mounted on an alumina substrate for home
projects.
This takes care of the tricky detail of soldering things directly to
the LED.
Ordinary soldering can be done to the pads on the alumina substrate.
https://www.kge.ca/en/product/lighting/22022-star-base-led-20mm-x-20-
mm-3w-aluminium-pcb.html
https://www.kge.ca/DATA/PRODUIT/22022~v~star-base-led-20mm-x-20-
mm-3w-aluminium-pcb.pdf
3.8V @ 750mA WW = warm white, thicker phosphor, 210 lumens >>> W = blue white, thinner phosphor, 230 lumens
At that power level, the star substrate gets hot, and should be fastened >>> to a piece of scrap metal for cooling purposes.
Using the smaller LEDs and making an array of LEDs, is a bit better with >>> regard to cooling issues. But it also takes a lot of resistors (which
are
needed to control and limit current flow). Some suppliers of electronic
compoents, charge 20x as much for resistors as other companies, so you
don't buy your bulk leaded resistors from boutique stores that charge
too much.
$0.05 per resistor, $0.20 per small T1 3/4 LED, is enough expense.
Super-high-power LEDs are not eye-safe, so use a diffuser to lessen
the risk of eye damage.
The above is not exactly a recipe-grade set of instructions. It's
the beginning of an illustration how to proceed, but many details
must be worked out. Your first circuit will have one tiny LED and
the circuit will not draw a lot of power. You work your way up, scaling
and testing as you go, until you learn how to assemble and drive larger
loads (as a hobbyist).
Paul
was looking for something that looked acceptable to SWMBO when fixed
on a wall.
The amusing part is that recommended 555 timer pre-dates you.
First marketed by Signetics in 1972.
I remember them being all new and shiny.
Something that may be of use here or elsewhere is the flexible LED
striplight which is cheap and easily available. It generally has sets
of three LEDs in series fed from 12V, which can be modified by careful
track cutting and different resistors to run on 5V.
On 2025-05-20, Joe <[email protected]> wrote:
Something that may be of use here or elsewhere is the flexible LED striplight which is cheap and easily available. It generally has
sets of three LEDs in series fed from 12V, which can be modified by
careful track cutting and different resistors to run on 5V.
If any of those USB chargers are USB C type then they might not be
limited to 5v and even so a 5V to 12V buck converter module can be
found for pennies.
On 21 May 2025 16:09:26 GMT
Bernard Peek <[email protected]> wrote:
On 2025-05-20, Joe <[email protected]> wrote:The USB supply is a USB-A on a computer. I'm willing to bet that will
Something that may be of use here or elsewhere is the flexible LED
striplight which is cheap and easily available. It generally has
sets of three LEDs in series fed from 12V, which can be modified by
careful track cutting and different resistors to run on 5V.
If any of those USB chargers are USB C type then they might not be
limited to 5v and even so a 5V to 12V buck converter module can be
found for pennies.
stick to 5V.
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