Grounding Issue
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Posts: 46,084
Hi folks!
I'm using a BS2 on a Super Carrier to control a BS1 Rev.D, which in
turn controls a couple of relays that turn LED's on and off. All of
the controlled circuitry (relays, LEDs, associated wiring) is on a
separate breadboard because the Rev.D's prototype area is too small.
The BS1-to-breadboard connections are:
1.BS1 5VDC to breadboard common power strip, 2. four(4) stamp pins
to relay set and reset pins for switching signals, and 3.BS1 ground
pin to breadboard common ground strip.
Another pin on the BS1 is connected to a pin on the BS2 for serial
control signals, and the BS1 ground is also connected to the BS2 VSS.
Now the strange part; the system only works properly when the BS1-
to-breadboard ground line is DISCONNECTED. When I hook it up, I get
inconsistently bad results.
You may wonder why I ask, when I know how to make it work!?!
Because I want to get an OEM BS1 and make a custom PCB to put all but
the BS2 on a single module. This means that the previous BS1-to-
breadboard ground, which seems to cause the trouble, will now be
permanent. If I can't find out why it's messing up under this
condition, I'm toast. By the way, the breadboard ground strip is NOT
connected to any other external ground.
Could it have anything to do with the fact that, when the BS1-to-
breadboard ground is hooked up, it is also directly connected to the
BS2 VSS? I can't disconnect the BS1-ground-to-BS2-VSS line, as then
I lose all serial comm for control signals.
I hope this is clear enough to understand the problem.
Any ideas?
Thanks
Don
I'm using a BS2 on a Super Carrier to control a BS1 Rev.D, which in
turn controls a couple of relays that turn LED's on and off. All of
the controlled circuitry (relays, LEDs, associated wiring) is on a
separate breadboard because the Rev.D's prototype area is too small.
The BS1-to-breadboard connections are:
1.BS1 5VDC to breadboard common power strip, 2. four(4) stamp pins
to relay set and reset pins for switching signals, and 3.BS1 ground
pin to breadboard common ground strip.
Another pin on the BS1 is connected to a pin on the BS2 for serial
control signals, and the BS1 ground is also connected to the BS2 VSS.
Now the strange part; the system only works properly when the BS1-
to-breadboard ground line is DISCONNECTED. When I hook it up, I get
inconsistently bad results.
You may wonder why I ask, when I know how to make it work!?!
Because I want to get an OEM BS1 and make a custom PCB to put all but
the BS2 on a single module. This means that the previous BS1-to-
breadboard ground, which seems to cause the trouble, will now be
permanent. If I can't find out why it's messing up under this
condition, I'm toast. By the way, the breadboard ground strip is NOT
connected to any other external ground.
Could it have anything to do with the fact that, when the BS1-to-
breadboard ground is hooked up, it is also directly connected to the
BS2 VSS? I can't disconnect the BS1-ground-to-BS2-VSS line, as then
I lose all serial comm for control signals.
I hope this is clear enough to understand the problem.
Any ideas?
Thanks
Don
Comments
of the electronics Gurus out there can give some ideas! Please see my
question below. I welcome any suggestions!
Thanks
Don
Sent: Sunday, June 02, 2002 9:23 AM
Subject: [noparse][[/noparse]basicstamps] Grounding Issue
> Hi folks!
> I'm using a BS2 on a Super Carrier to control a BS1 Rev.D, which in
> turn controls a couple of relays that turn LED's on and off. All of
> the controlled circuitry (relays, LEDs, associated wiring) is on a
> separate breadboard because the Rev.D's prototype area is too small.
> The BS1-to-breadboard connections are:
> 1.BS1 5VDC to breadboard common power strip, 2. four(4) stamp pins
> to relay set and reset pins for switching signals, and 3.BS1 ground
> pin to breadboard common ground strip.
> Another pin on the BS1 is connected to a pin on the BS2 for serial
> control signals, and the BS1 ground is also connected to the BS2 VSS.
> Now the strange part; the system only works properly when the BS1-
> to-breadboard ground line is DISCONNECTED. When I hook it up, I get
> inconsistently bad results.
> You may wonder why I ask, when I know how to make it work!?!
> Because I want to get an OEM BS1 and make a custom PCB to put all but
> the BS2 on a single module. This means that the previous BS1-to-
> breadboard ground, which seems to cause the trouble, will now be
> permanent. If I can't find out why it's messing up under this
> condition, I'm toast. By the way, the breadboard ground strip is NOT
> connected to any other external ground.
> Could it have anything to do with the fact that, when the BS1-to-
> breadboard ground is hooked up, it is also directly connected to the
> BS2 VSS? I can't disconnect the BS1-ground-to-BS2-VSS line, as then
> I lose all serial comm for control signals.
> I hope this is clear enough to understand the problem.
> Any ideas?
> Thanks
> Don
to drive the relays. You may be marginally driving the relays due to the
current output limitations of the Stamps I/O pins.
relay coil is rated 5 VDC, 40 mA, 125 Ohm. I have read up on transistors
but I still don't understand them well enough to pick one.
Don
Original Message
From: <azeasi@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, June 03, 2002 7:03 PM
Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
> You should not drive relays directly with the stamp. Use a transistor
switch
> to drive the relays. You may be marginally driving the relays due to the
> current output limitations of the Stamps I/O pins.
>
> 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.
>
>
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>
>
>
OHM resistor in series with base connection (will limit I drawn from
chip to approx 1mA), and don't forget a back EMF diode across the relay
coil (1N4000 or any of the 1N4*** series will do).
ROB
Original Message
From: Don [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=Nuoo5mXCO4DZ0xnVgwPAQdDCG882CB_ij08tJQEl1B_X17IqkDCMDvlgI8ZcymFUkVAXCCDWaBYl9WD5GS5GNxpG7-Y]renegade.engineer@v...[/url
Sent: 04 June 2002 15:26
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
Ok, I could use some help figuring out what transistor to use. The
relay coil is rated 5 VDC, 40 mA, 125 Ohm. I have read up on
transistors
but I still don't understand them well enough to pick one.
Don
Original Message
From: <azeasi@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, June 03, 2002 7:03 PM
Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
> You should not drive relays directly with the stamp. Use a transistor
switch
> to drive the relays. You may be marginally driving the relays due to
the
> current output limitations of the Stamps I/O pins.
>
> 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/
>
>
>
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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Ground the source pin.
Tie the gate to the stamp pin, no resistor is required as the mosfet's gate
load is less than a microamp at dc and only a small capacitive load, if you
prefer you could use a resistor anything from 470 ohms through 1 meg will
do. (I personally use a 10K if anything, because I accidentally ordered ten
thousand 10,000 ohm resistors).
Tie the drain lead to the relay coil, and put a diode across the coil
(reverse biased) to limit inductive kickback.
Original Message
From: "Don" <renegade.engineer@
> Ok, I could use some help figuring out what transistor to use. The
> relay coil is rated 5 VDC, 40 mA, 125 Ohm. I have read up on transistors
> but I still don't understand them well enough to pick one.
> Don
>
Original Message
> From: <azeasi@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, June 03, 2002 7:03 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
>
>
> > You should not drive relays directly with the stamp. Use a transistor
> switch
> > to drive the relays. You may be marginally driving the relays due to the
> > current output limitations of the Stamps I/O pins.
> >
> > 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/
> >
> >
> >
>
>
>
> 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/
>
>
Don
Original Message
From: "Rob" <robbed666@b...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, June 04, 2002 8:51 AM
Subject: RE: [noparse][[/noparse]basicstamps] Grounding Issue
> BC337, BC107, 2N3904, BC107,8,9 all NPN devices with HFE >50. Put a 4.7K
> OHM resistor in series with base connection (will limit I drawn from
> chip to approx 1mA), and don't forget a back EMF diode across the relay
> coil (1N4000 or any of the 1N4*** series will do).
>
> ROB
>
>
Original Message
> From: Don [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=2hdj3Bsm6B-YFH-rPs4HfBP6vnn8T5PmK17PfAZDCmOq5yN0jhgAnc47fJbJDDeE4H0zbnFutLL3PnkOZLdg4BkahOmLDw]renegade.engineer@v...[/url
> Sent: 04 June 2002 15:26
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
>
> Ok, I could use some help figuring out what transistor to use. The
> relay coil is rated 5 VDC, 40 mA, 125 Ohm. I have read up on
> transistors
> but I still don't understand them well enough to pick one.
> Don
>
Original Message
> From: <azeasi@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, June 03, 2002 7:03 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
>
>
> > You should not drive relays directly with the stamp. Use a transistor
> switch
> > to drive the relays. You may be marginally driving the relays due to
> the
> > current output limitations of the Stamps I/O pins.
> >
> > 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/
> >
> >
> >
>
>
>
> 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.
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>
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
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>
>
>
Don
Original Message
From: "FalconWireless Tech Support - KF4HAZ"
<techsupport@f...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, June 04, 2002 9:17 AM
Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
> My personal preference is the 2n7000 mosfet. ($4.00 / hundred)
> Ground the source pin.
>
> Tie the gate to the stamp pin, no resistor is required as the mosfet's
gate
> load is less than a microamp at dc and only a small capacitive load, if
you
> prefer you could use a resistor anything from 470 ohms through 1 meg will
> do. (I personally use a 10K if anything, because I accidentally ordered
ten
> thousand 10,000 ohm resistors).
>
> Tie the drain lead to the relay coil, and put a diode across the coil
> (reverse biased) to limit inductive kickback.
>
>
Original Message
> From: "Don" <renegade.engineer@
>
> > Ok, I could use some help figuring out what transistor to use. The
> > relay coil is rated 5 VDC, 40 mA, 125 Ohm. I have read up on
transistors
> > but I still don't understand them well enough to pick one.
> > Don
> >
Original Message
> > From: <azeasi@a...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Monday, June 03, 2002 7:03 PM
> > Subject: Re: [noparse][[/noparse]basicstamps] Grounding Issue
> >
> >
> > > You should not drive relays directly with the stamp. Use a transistor
> > switch
> > > to drive the relays. You may be marginally driving the relays due to
the
> > > current output limitations of the Stamps I/O pins.
> > >
> > > 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/
> > >
> > >
> > >
> >
> >
> >
> > 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/
> >
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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>
>
>
>My personal preference is the 2n7000 mosfet. ($4.00 / hundred)
Can you tell us the supplier for those FETs at that price?
dwayne
--
Dwayne Reid <dwayner@p...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 18 years of Engineering Innovation (1984 - 2002)
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Do you know of an online source for the 2n7000 mosfet? Thanks.
Scott
but...
"A $5 handling charge is added to your order if the subtotal is less than
$25."
Since the unit cost is only $0.31, that makes it one expensive MOSFET.
Don
Original Message
From: "southernpost" <Scott@b...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, June 05, 2002 11:39 AM
Subject: [noparse][[/noparse]basicstamps] Re: Grounding Issue
> Don -
>
> Do you know of an online source for the 2n7000 mosfet? Thanks.
>
> Scott
>
>
>
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>
>
>
transistor (2N3904) and a 1K or less 1/4 watt resistor to drive your relay.
If you insist on buying the 2N7000 part it won't work any better for your
application. You aren't concerned about nanosecond switching speeds! By the
way Web-Tronics.com also carries the 2N7000 at the 29 cent price as well as
the 2N3904 etc. I don't think they have a minimum but probably would not
appreciate an order for 29 cents!