Mosfet/hexfet?
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Posts: 46,084
Hi, I just joined this group and have learned a bunch just reading
the posts but had a couple of questions. I am attempting to design a
circuit that I hope to control with a basic stamp. Hopefully, the
stamp will control a couple of solenoids and I'm pretty sure that the
solenoids draw too many amps to be used without a MOSFET or some
other switch. I've been reading about the various types and have
given up on the hope that the local Radio Shack will ever receive the
IRF510 that I ordered months ago. I have been browsing a catalog and
see MOSFET's and HEXFET's, are they the same? I'm not sure at this
point how many amps the solenoids will draw or what solenoid I will
be using yet so I'm still window shopping. Any guidance would be
appreciated. Thanks
the posts but had a couple of questions. I am attempting to design a
circuit that I hope to control with a basic stamp. Hopefully, the
stamp will control a couple of solenoids and I'm pretty sure that the
solenoids draw too many amps to be used without a MOSFET or some
other switch. I've been reading about the various types and have
given up on the hope that the local Radio Shack will ever receive the
IRF510 that I ordered months ago. I have been browsing a catalog and
see MOSFET's and HEXFET's, are they the same? I'm not sure at this
point how many amps the solenoids will draw or what solenoid I will
be using yet so I'm still window shopping. Any guidance would be
appreciated. Thanks
Comments
of
them;
http://www.glitchbuster.com
> Hi, I just joined this group and have learned a bunch just reading
> the posts but had a couple of questions. I am attempting to design a
> circuit that I hope to control with a basic stamp. Hopefully, the
> stamp will control a couple of solenoids and I'm pretty sure that the
> solenoids draw too many amps to be used without a MOSFET or some
> other switch. I've been reading about the various types and have
> given up on the hope that the local Radio Shack will ever receive the
> IRF510 that I ordered months ago. I have been browsing a catalog and
> see MOSFET's and HEXFET's, are they the same? I'm not sure at this
> point how many amps the solenoids will draw or what solenoid I will
> be using yet so I'm still window shopping. Any guidance would be
> appreciated. Thanks
[noparse][[/noparse]Non-text portions of this message have been removed]
smartdim@a... writes:
>
> There are logic level MOSFETS such as the IRL540N(36A). Here is one
> supplier
> of
> them;
> http://www.glitchbuster.com
OR www.digikey.com
[noparse][[/noparse]Non-text portions of this message have been removed]
Detail.jsp?id=06F8237
only 71 cents a piece too.
I get all my stuff from Newark. You have to pay a few bucks for shipping,
so you might as well go all out and order 10 of those FETs just because it
is inevitable that you'll screw one up somehow [noparse]:)[/noparse]
-- Kyle S.
Original Message
From: <hilokine@g...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, December 17, 2002 8:51 PM
Subject: [noparse][[/noparse]basicstamps] MOSFET/HEXFET?
> Hi, I just joined this group and have learned a bunch just reading
> the posts but had a couple of questions. I am attempting to design a
> circuit that I hope to control with a basic stamp. Hopefully, the
> stamp will control a couple of solenoids and I'm pretty sure that the
> solenoids draw too many amps to be used without a MOSFET or some
> other switch. I've been reading about the various types and have
> given up on the hope that the local Radio Shack will ever receive the
> IRF510 that I ordered months ago. I have been browsing a catalog and
> see MOSFET's and HEXFET's, are they the same? I'm not sure at this
> point how many amps the solenoids will draw or what solenoid I will
> be using yet so I'm still window shopping. Any guidance would be
> appreciated. Thanks
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
voltage? Or maybe their current rating? If so, we can help you select a
good MOSFET match for your project.
The IRF510 does not fully turn on with a "high" from a Stamp pin. It can
work okay sometimes, but there will be more resistance than if it was fully
on, which means that the transistor is using up some of the power that you
wanted to use in your load (solenoids in this case). That power turns into
heat in the transistor, and you might even end up needing a heat sink which
wouldn't have been required if the transistor was fully on. That's why I
really like the logic gate voltage MOSFETS. They're fully on with a Stamp
pin "high" output.
Common part numbers are:
IRL520N - 10A/100V
IRL530N - 17A/100V
IRL540N - 36A/100V
The current ratings are continuous, and brief peak currents can be
considerably higher. HEXFETs are an International Rectifier (IR) trademark
for their power MOSFET transistors. Since the above part numbers are from
IR, they are both MOSFETs and HEXFETs.
Since someone already mentioned www.glitchbuster.com, I'll admit it --
that's me. Pricing, for example, on the IRL530N is 0.99 vs. 1.53 at
DigiKey. Shipping for any number of components is only $1.85, with no
minimum order. (I'm only mentioning this because pricing has been discussed
in previous posts to this thread, and hope this isn't against list
etiquette.)
Interesting email name... are you in HI, or the pacific islands?
Randy Jones
www.glitchbuster.com
(A happy Parallax customer since 1993)
Original Message
From: <hilokine@g...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, December 17, 2002 5:51 PM
Subject: [noparse][[/noparse]basicstamps] MOSFET/HEXFET?
> Hi, I just joined this group and have learned a bunch just reading
> the posts but had a couple of questions. I am attempting to design a
> circuit that I hope to control with a basic stamp. Hopefully, the
> stamp will control a couple of solenoids and I'm pretty sure that the
> solenoids draw too many amps to be used without a MOSFET or some
> other switch. I've been reading about the various types and have
> given up on the hope that the local Radio Shack will ever receive the
> IRF510 that I ordered months ago. I have been browsing a catalog and
> see MOSFET's and HEXFET's, are they the same? I'm not sure at this
> point how many amps the solenoids will draw or what solenoid I will
> be using yet so I'm still window shopping. Any guidance would be
> appreciated. Thanks
order for it to turn on.
That way you can also control the current from the stamp since it can only
source 20mA (bs2). I think a 330 ohm resistor will limit the high signal to
15 mA, then you can just step up the voltage. It also provides somewhat of
a buffer between the solenoid and the FET, which gives you a better chance
of not frying your stamp.
Original Message
From: "Randy Jones" <randyjones@w...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, December 18, 2002 12:25 PM
Subject: Re: [noparse][[/noparse]basicstamps] MOSFET/HEXFET?
> Hi... Do you know the resistance of the solenoid, and the operating
> voltage? Or maybe their current rating? If so, we can help you select a
> good MOSFET match for your project.
>
> The IRF510 does not fully turn on with a "high" from a Stamp pin. It can
> work okay sometimes, but there will be more resistance than if it was
fully
> on, which means that the transistor is using up some of the power that you
> wanted to use in your load (solenoids in this case). That power turns
into
> heat in the transistor, and you might even end up needing a heat sink
which
> wouldn't have been required if the transistor was fully on. That's why I
> really like the logic gate voltage MOSFETS. They're fully on with a Stamp
> pin "high" output.
>
> Common part numbers are:
>
> IRL520N - 10A/100V
> IRL530N - 17A/100V
> IRL540N - 36A/100V
>
> The current ratings are continuous, and brief peak currents can be
> considerably higher. HEXFETs are an International Rectifier (IR)
trademark
> for their power MOSFET transistors. Since the above part numbers are from
> IR, they are both MOSFETs and HEXFETs.
>
> Since someone already mentioned www.glitchbuster.com, I'll admit it --
> that's me. Pricing, for example, on the IRL530N is 0.99 vs. 1.53 at
> DigiKey. Shipping for any number of components is only $1.85, with no
> minimum order. (I'm only mentioning this because pricing has been
discussed
> in previous posts to this thread, and hope this isn't against list
> etiquette.)
>
> Interesting email name... are you in HI, or the pacific islands?
>
> Randy Jones
> www.glitchbuster.com
> (A happy Parallax customer since 1993)
>
>
Original Message
> From: <hilokine@g...>
> To: <basicstamps@yahoogroups.com>
> Sent: Tuesday, December 17, 2002 5:51 PM
> Subject: [noparse][[/noparse]basicstamps] MOSFET/HEXFET?
>
>
> > Hi, I just joined this group and have learned a bunch just reading
> > the posts but had a couple of questions. I am attempting to design a
> > circuit that I hope to control with a basic stamp. Hopefully, the
> > stamp will control a couple of solenoids and I'm pretty sure that the
> > solenoids draw too many amps to be used without a MOSFET or some
> > other switch. I've been reading about the various types and have
> > given up on the hope that the local Radio Shack will ever receive the
> > IRF510 that I ordered months ago. I have been browsing a catalog and
> > see MOSFET's and HEXFET's, are they the same? I'm not sure at this
> > point how many amps the solenoids will draw or what solenoid I will
> > be using yet so I'm still window shopping. Any guidance would be
> > appreciated. Thanks
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
current from the Stamp pin. There is no need to regulate it, and no worry
about frying the Stamp. That's why I really like them, especially the
logic-level gate voltage units.
They also don't have the built-in voltage drop that a Darlington has. This
means you get more power to your load, and less heat in the transistor.
If you did have some standard MOSFETs without the logic level gate voltage,
you could also use an inexpensive general purpose transistor and a pull-up
resistor between the Stamp and the MOSFET to control the higher gate
voltage. That would be easier and cheaper than an op-amp.
Randy
www.glitchbuster.com
> you can always use some op-amps to step op the gate voltage to the MOSFET
in
> order for it to turn on.
> That way you can also control the current from the stamp since it can only
> source 20mA (bs2). I think a 330 ohm resistor will limit the high signal
to
> 15 mA, then you can just step up the voltage. It also provides somewhat
of
> a buffer between the solenoid and the FET, which gives you a better chance
> of not frying your stamp.
why they work, also meaning that 0 dc current goes into the FET, however,
you can never be sure you won't get feed back from them, especially when the
solenoids shut off and there will be enormous current spikes. The only way
to truly isolate the stamp is using a photo FET optocoupler (ie H11F1,
H11F2, H11F3 by fairchild semiconductor). I use them for almost every
output pin in order to isolate....maybe I'm just being conservative and
over-protective. Just my opinion, though I do agree with you that in
general you shouldn't have to worry about the current draw when using
MOSFETs (I don't want to start a flame, I just wanted to share my
perspective).
-- Kyle S.
P.S. This list is great, I've learned a lot from everyone. Thanks to all
who contribute!
> The MOSFETs have a very high gate resistance, so they draw nearly zero
> current from the Stamp pin. There is no need to regulate it, and no worry
> about frying the Stamp. That's why I really like them, especially the
> logic-level gate voltage units.
>
> They also don't have the built-in voltage drop that a Darlington has.
This
> means you get more power to your load, and less heat in the transistor.
>
> If you did have some standard MOSFETs without the logic level gate
voltage,
> you could also use an inexpensive general purpose transistor and a pull-up
> resistor between the Stamp and the MOSFET to control the higher gate
> voltage. That would be easier and cheaper than an op-amp.
>
> Randy
> www.glitchbuster.com
>
> > you can always use some op-amps to step op the gate voltage to the
MOSFET
> in
> > order for it to turn on.
> > That way you can also control the current from the stamp since it can
only
> > source 20mA (bs2). I think a 330 ohm resistor will limit the high
signal
> to
> > 15 mA, then you can just step up the voltage. It also provides
somewhat
> of
> > a buffer between the solenoid and the FET, which gives you a better
chance
> > of not frying your stamp.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
randyjones@w... writes:
> The MOSFETs have a very high gate resistance, so they draw nearly zero
> current from the Stamp pin. There is no need to regulate it, and no worry
> about frying the Stamp. That's why I really like them, especially the
> logic-level gate voltage units.
>
> They also don't have the built-in voltage drop that a Darlington has. This
> means you get more power to your load, and less heat in the transistor.
>
> If you did have some standard MOSFETs without the logic level gate voltage,
> you could also use an inexpensive general purpose transistor and a pull-up
> resistor between the Stamp and the MOSFET to control the higher gate
> voltage. That would be easier and cheaper than an op-amp.
>
> Randy
> www.glitchbuster.com
Thats right!!
[noparse][[/noparse]Non-text portions of this message have been removed]
KamaolaKid@g... writes:
> Yes, I know, in theory MOSFETs have an infinite gate resistance.... that is
> why they work, also meaning that 0 dc current goes into the FET, however,
> you can never be sure you won't get feed back from them, especially when
> the
> solenoids shut off and there will be enormous current spikes. The only way
> to truly isolate the stamp is using a photo FET optocoupler (ie H11F1,
> H11F2, H11F3 by fairchild semiconductor). I use them for almost every
> output pin in order to isolate....maybe I'm just being conservative and
> over-protective. Just my opinion, though I do agree with you that in
> general you shouldn't have to worry about the current draw when using
> MOSFETs (I don't want to start a flame, I just wanted to share my
> perspective).
>
> -- Kyle S.
>
> P.S. This list is great, I've learned a lot from everyone. Thanks to all
> who contribute!
Also true, but most MOSFETS have a "reverse spike" diode that will clamp the
flyback voltage. Opto-isolating is a very safe way to go however if you are
paraniod!
[noparse][[/noparse]Non-text portions of this message have been removed]
reference and appreciate the tips. I had been told previously on a
different board that I should use a "Logic Level" MOSFET but could
never get an answer what that meant. Now at least I have a feel for
what to look for. RANDY: I will most probably be contacting you to
purchase a few of those MOSFET's, do you accept paypal? By the way,
do you sell push or pull tubular solenoids? Also, yes, I am in
Hawaii... sunny Blue skies, beautiful sunsets, cool beaches...but
these darn Hula Girls always bumping into you ;-)
HAPPY HOLIDAYS ALL!!!
--- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> In a message dated 12/18/2002 10:51:27 AM Pacific Standard Time,
> KamaolaKid@g... writes:
>
> > Yes, I know, in theory MOSFETs have an infinite gate
resistance.... that is
> > why they work, also meaning that 0 dc current goes into the FET,
however,
> > you can never be sure you won't get feed back from them,
especially when
> > the
> > solenoids shut off and there will be enormous current spikes.
The only way
> > to truly isolate the stamp is using a photo FET optocoupler (ie
H11F1,
> > H11F2, H11F3 by fairchild semiconductor). I use them for almost
every
> > output pin in order to isolate....maybe I'm just being
conservative and
> > over-protective. Just my opinion, though I do agree with you
that in
> > general you shouldn't have to worry about the current draw when
using
> > MOSFETs (I don't want to start a flame, I just wanted to share my
> > perspective).
> >
> > -- Kyle S.
> >
> > P.S. This list is great, I've learned a lot from everyone.
Thanks to all
> > who contribute!
>
> Also true, but most MOSFETS have a "reverse spike" diode that will
clamp the
> flyback voltage. Opto-isolating is a very safe way to go however if
you are
> paraniod!
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
Yes... and you seem sooo upset about that -- heh, heh!! PayPal is fine...
feel free to email off-list and I'll send you the details.
Kyle... I understand about the gate capacitance issue, and isolating under
certain conditions with optos. I got the impression from your first message
that you were talking about continuous current (maybe I read it too fast
this morning). I think in many cases it comes down to how conservative your
design needs to be, and the particular situation. For my typical projects I
have generally found no isolation necessary, although a 50 to 100 ohm series
resistor near the gate is often recommended to minimize the chance of
oscillation. Now if you were designing critical medical equipment, that
would probably be a different story -- bring out the belt and suspenders!
Randy
www.glitchbuster.com