Wattage

B

Bobby

Guest
I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12 watts.

How do I label this device so that a lay person will understand its maximum
operating capacity should not exceed 1 amp, depending on their selected
operating voltage?

Most lay users seem to look at wattage and assume that the indicated wattage
is for 12 or 24 volt operation.

Any suggestion appreciated.
 
On Sun, 03 Feb 2008 08:37:57 GMT, "Bobby" <bob@bobsville.com> wrote:

I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12 watts.

How do I label this device so that a lay person will understand its maximum
operating capacity should not exceed 1 amp, depending on their selected
operating voltage?
Click to expand...
---
Don't you mean:

"How do I label this device so that a lay person will understand its
maximum output current will not exceed 1 amp, regardless of their
selected operating voltage?"


Make it a no-brainer and take the responsibility for overloading it
out of their hands by building a 1 amp current limiting circuit into
the device and then labeling it: "OUTPUT CURRENT INTERNALLY LIMITED
TO 1 AMPERE" or something like that.
 
On Sun, 03 Feb 2008 08:37:57 GMT, "Bobby" <bob@bobsville.com> wrote:

I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12 watts.
Click to expand...
---
I missed it earlier, but that's not necessarily true since the power
being dissipated will depend on the voltage being dropped across the
MOSFET and the current through it.

What does your circuit look like?
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:felbq31oqhe30og2on262korcs82hsecng@4ax.com...
On Sun, 03 Feb 2008 08:37:57 GMT, "Bobby" <bob@bobsville.com> wrote:

I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as
the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12
watts.

How do I label this device so that a lay person will understand its
maximum
operating capacity should not exceed 1 amp, depending on their selected
operating voltage?

---
Don't you mean:

"How do I label this device so that a lay person will understand its
maximum output current will not exceed 1 amp, regardless of their
selected operating voltage?"
Click to expand...
Yes John, That is exactly what I mean
Make it a no-brainer and take the responsibility for overloading it
out of their hands by building a 1 amp current limiting circuit into
the device and then labeling it: "OUTPUT CURRENT INTERNALLY LIMITED
TO 1 AMPERE" or something like that.

I would love to do this but unfortunatley I am only the manufacturer of this
Click to expand...
device and make but a few pennies from it.
The middle man makes a fair wack and only complains about cost - the usual
scenario!
The circuit is kept to its bare-bones.
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:l5nbq3dnhan47s8gd2csr1faqbtsomkljr@4ax.com...
On Sun, 03 Feb 2008 08:37:57 GMT, "Bobby" <bob@bobsville.com> wrote:

I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as
the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12
watts.

---
I missed it earlier, but that's not necessarily true since the power
being dissipated will depend on the voltage being dropped across the
MOSFET and the current through it.

What does your circuit look like?

Hi John,
Click to expand...

The circuit is simple, goes like this:
1) 12/24V into a 78LS05 supplying a PIC10F202.
2) GPIO,0 connected to gate of FET via 100ohm
3) GPIO,1,2,3 used as inputs to govern output speed, style and run/pause
4) The 12/24 volts (+) as common output with return cct into FET.
Thats it.

The user might connect 12 or 24 volt lamps to the output terminals (FET).
Due to size restrictions the FET cannot be heatsinked therefore 1 amp is
optimum maximum before any significant heating occurs.

If I could supply the DC power pack with the unit that would help, however
knowing end users as I do they would soon figure out that they could connect
a heavier power supply (auto battery!!).

Something just occured to me, I wonder if there exists a self resetting fuse
at a reasonable price???

Thanks for your input.
 
"Bobby" <bob@bobsville.com> wrote in message
news:F3fpj.10566$421.9994@news-server.bigpond.net.au...
I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as
the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12
watts.

How do I label this device so that a lay person will understand its
maximum
operating capacity should not exceed 1 amp, depending on their selected
operating voltage?

Most lay users seem to look at wattage and assume that the indicated
wattage
is for 12 or 24 volt operation.

Any suggestion appreciated.
Click to expand...

Put a fuse, if someone blew it up, he will learn from his mistake. Cheap
solution for you and him...Heehee.......
 
"Bobby" <bob@bobsville.com> wrote in message
news:RVzpj.10965$421.8747@news-server.bigpond.net.au...
"John Fields" <jfields@austininstruments.com> wrote in message
news:l5nbq3dnhan47s8gd2csr1faqbtsomkljr@4ax.com...
On Sun, 03 Feb 2008 08:37:57 GMT, "Bobby" <bob@bobsville.com> wrote:

I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement
to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as
the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12
watts.

---
I missed it earlier, but that's not necessarily true since the power
being dissipated will depend on the voltage being dropped across the
MOSFET and the current through it.

What does your circuit look like?

Hi John,

The circuit is simple, goes like this:
1) 12/24V into a 78LS05 supplying a PIC10F202.
2) GPIO,0 connected to gate of FET via 100ohm
3) GPIO,1,2,3 used as inputs to govern output speed, style and run/pause
4) The 12/24 volts (+) as common output with return cct into FET.
Thats it.

The user might connect 12 or 24 volt lamps to the output terminals (FET).
Due to size restrictions the FET cannot be heatsinked therefore 1 amp is
optimum maximum before any significant heating occurs.

If I could supply the DC power pack with the unit that would help,
however
knowing end users as I do they would soon figure out that they could
connect
a heavier power supply (auto battery!!).

Something just occured to me, I wonder if there exists a self resetting
fuse
at a reasonable price???
Click to expand...

I use a sensitive circuit breaker on my power supply, this is my protection
because I overloaded my circuit many hundreds times for testing hi-power
circuits etc.. It never fails me.
 
On Mon, 04 Feb 2008 08:21:05 GMT, "Bobby" <bob@bobsville.com> wrote:


Something just occured to me, I wonder if there exists a self resetting fuse
at a reasonable price???
Click to expand...
---
http://www.circuitprotection.com/polyswitch.asp

--
JF
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:mf4eq3lohl21p2ihq2u98sa2ndd2ln4n43@4ax.com...
On Mon, 04 Feb 2008 08:21:05 GMT, "Bobby" <bob@bobsville.com> wrote:


Something just occured to me, I wonder if there exists a self resetting
fuse
at a reasonable price???

---
http://www.circuitprotection.com/polyswitch.asp

--
JF
Click to expand...


Thanks John, they are very nice, but are they reasonable in prices?
 
On Mon, 4 Feb 2008 13:13:50 -0800, "Jakthehammer"
<jakthhmmr@aol.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:mf4eq3lohl21p2ihq2u98sa2ndd2ln4n43@4ax.com...
On Mon, 04 Feb 2008 08:21:05 GMT, "Bobby" <bob@bobsville.com> wrote:


Something just occured to me, I wonder if there exists a self resetting
fuse
at a reasonable price???

---
http://www.circuitprotection.com/polyswitch.asp

--
JF



Thanks John, they are very nice, but are they reasonable in prices?
Click to expand...
Hell, since what's reasonable for me might be outrageous for you,
how should I know???

Check their distributors.
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:mf4eq3lohl21p2ihq2u98sa2ndd2ln4n43@4ax.com...
On Mon, 04 Feb 2008 08:21:05 GMT, "Bobby" <bob@bobsville.com> wrote:


Something just occured to me, I wonder if there exists a self resetting
fuse
at a reasonable price???

---
http://www.circuitprotection.com/polyswitch.asp

--
JF
I've decided to use this option - quite affordable (+/-1A/30V = $AU$1.26)
Click to expand...

Now the next problem.........
A circuit having three outputs (FETs), same scenario as previous, each
output to limit 1A.
Now, do I use 1 overall polyswitch at 3A or one 1A per output ??

If a 3A poly is used and a user decides to use only one of the outputs, but
loads it to 2.5/3A the poly won't help, as that output FET will fry!
So I suppose to hell with cost, it'll have to be one x 1A per output!!

Thanks for the info on the Polyswitches John - you've been a great help.
 
On Tue, 05 Feb 2008 09:30:40 GMT, "Bobby" <bob@bobsville.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:mf4eq3lohl21p2ihq2u98sa2ndd2ln4n43@4ax.com...
On Mon, 04 Feb 2008 08:21:05 GMT, "Bobby" <bob@bobsville.com> wrote:


Something just occured to me, I wonder if there exists a self resetting
fuse
at a reasonable price???

---
http://www.circuitprotection.com/polyswitch.asp

--
JF
I've decided to use this option - quite affordable (+/-1A/30V = $AU$1.26)

Now the next problem.........
A circuit having three outputs (FETs), same scenario as previous, each
output to limit 1A.
Now, do I use 1 overall polyswitch at 3A or one 1A per output ??

If a 3A poly is used and a user decides to use only one of the outputs, but
loads it to 2.5/3A the poly won't help, as that output FET will fry!
So I suppose to hell with cost, it'll have to be one x 1A per output!!
Click to expand...
---
Yup.
---
Thanks for the info on the Polyswitches John - you've been a great help.
Click to expand...
---
My pleasure! :)
 
"Jakthehammer" <jakthhmmr@aol.com> wrote in message
news:fo6ptl$8g9$1@aioe.org...
Put a fuse, if someone blew it up, he will learn from his mistake. Cheap
solution for you and him...Heehee.......
Click to expand...
Unfortunately knowing end users as I do, they will replace the 1A fuse with
a six inch nail, then when the unit melts I'll get the blame!
 
"Bobby" <bob@bobsville.com> wrote in message
news:lo4qj.11611$421.8975@news-server.bigpond.net.au...
"Jakthehammer" <jakthhmmr@aol.com> wrote in message
news:fo6ptl$8g9$1@aioe.org...
Put a fuse, if someone blew it up, he will learn from his mistake.
Cheap
solution for you and him...Heehee.......

Unfortunately knowing end users as I do, they will replace the 1A fuse
with
a six inch nail, then when the unit melts I'll get the blame!
Click to expand...



That's a good point. The AutoReset Fuse maybe handy, no one can tamp with
it.
 
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