Proximity Switch and count Function
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I am trying to build a wind speed indicator and decided to use a
proximity switch and a Basic Stamp 2 to count the switch closures and
then calibrate the wind speed from the total count. The problem I am
having is I can not get a consistent reading from the proximity
switch. The readings are all over the map (From 0 sometimes up to 150)
as I try and trigger the prox. The code I am using is as follows:
'($StampBS2)
Speed Var Word
Again:
Count 1, 500, Speed
Debug CLS, Dec ?, Speed
Low 1
Goto Again
Note I had to add the Low 1 command to get any type of reading. Any
help would be appreaciated.
Thanks Loren
proximity switch and a Basic Stamp 2 to count the switch closures and
then calibrate the wind speed from the total count. The problem I am
having is I can not get a consistent reading from the proximity
switch. The readings are all over the map (From 0 sometimes up to 150)
as I try and trigger the prox. The code I am using is as follows:
'($StampBS2)
Speed Var Word
Again:
Count 1, 500, Speed
Debug CLS, Dec ?, Speed
Low 1
Goto Again
Note I had to add the Low 1 command to get any type of reading. Any
help would be appreaciated.
Thanks Loren
Comments
you refer to is a magnetic reed switch, it will tend to bounce a
number of times as it closes and give you multiple counts where you
expect only one. You can "debounce" it with a resistor and a
capacitor:
2.2k switch
_
+Vdd ----/\/\
o o
o---Vss common
|
1k |
P0 ----o----/\/\
o
| |
===== 0.1 debounce |
| |
`
'
-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com
>I am trying to build a wind speed indicator and decided to use a
>proximity switch and a Basic Stamp 2 to count the switch closures and
>then calibrate the wind speed from the total count. The problem I am
>having is I can not get a consistent reading from the proximity
>switch. The readings are all over the map (From 0 sometimes up to 150)
>as I try and trigger the prox. The code I am using is as follows:
>
>'($StampBS2)
>Speed Var Word
>Again:
>Count 1, 500, Speed
>Debug CLS, Dec ?, Speed
>Low 1
>Goto Again
>
>Note I had to add the Low 1 command to get any type of reading. Any
>help would be appreaciated.
>Thanks Loren
on the high side of the switch, not on ground.
Clark Hughes
Tracy Allen wrote:
>
> The problem may be in the hardware hookup. If the proximity switch
> you refer to is a magnetic reed switch, it will tend to bounce a
> number of times as it closes and give you multiple counts where you
> expect only one. You can "debounce" it with a resistor and a
> capacitor:
>
> 2.2k switch
> _
> +Vdd ----/\/\
o o
o---Vss common
> |
> 1k |
> P0 ----o----/\/\
o
> | |
> ===== 0.1 debounce |
> | |
> `
'
>
> -- regards,
> Tracy Allen
> electronically monitored ecosystems
> mailto:tracy@e...
> http://www.emesystems.com
>
>was to tap in on the high side of the switch, not on ground.
>Clark Hughes
Hi Clark, You're absolutely right. Here it is, moved over:
2.2k switch
_
+Vdd ----/\/\--o---o o
o---Vss common
|
1k |
P0 ----o----/\/\
o
| |
===== 0.1 |
| |
`
'
Too early in the morning. A professor I worked with told us always
to sneak an obvious error onto the blackboard at the beginning of a
lecture. There was bound to be somebody who would speak up about it,
and wake everyone up and open up discussion. If not, assume everyone
is already asleep!
-- Tracy
>
>
>Tracy Allen wrote:
>>
>> The problem may be in the hardware hookup. If the proximity switch
>> you refer to is a magnetic reed switch, it will tend to bounce a
>> number of times as it closes and give you multiple counts where you
>> expect only one. You can "debounce" it with a resistor and a
>> capacitor:
>>
>
> > 2.2k switch
>> _
>> +Vdd ----/\/\
o o
o---Vss common
>> |
>> 1k |
>> P0 ----o----/\/\
o
>> | |
>> ===== 0.1 debounce |
>> | |
>> `
'
> >
>> -- regards,
>> Tracy Allen
>> electronically monitored ecosystems
>> mailto:tracy@e...
> > http://www.emesystems.com
>>
>
coming from the prox switch. Power, ground, and the load, where do I
put the resistor and the capacitor.
Thanks Loren
--- In basicstamps@y..., Tracy Allen <tracy@e...> wrote:
> >Might want to double check that schematic. I think the intention
> >was to tap in on the high side of the switch, not on ground.
> >Clark Hughes
>
> Hi Clark, You're absolutely right. Here it is, moved over:
>
> 2.2k switch
> _
> +Vdd ----/\/\--o---o o
o---Vss common
> |
> 1k |
> P0 ----o----/\/\
o
> | |
> ===== 0.1 |
> | |
> `
'
> Too early in the morning. A professor I worked with told us always
> to sneak an obvious error onto the blackboard at the beginning of a
> lecture. There was bound to be somebody who would speak up about
it,
> and wake everyone up and open up discussion. If not, assume
everyone
> is already asleep!
>
> -- Tracy
>
> >
> >
> >Tracy Allen wrote:
> >>
> >> The problem may be in the hardware hookup. If the proximity
switch
> >> you refer to is a magnetic reed switch, it will tend to bounce a
> >> number of times as it closes and give you multiple counts where
you
> >> expect only one. You can "debounce" it with a resistor and a
> >> capacitor:
> >>
> >
> > > 2.2k switch
> >> _
> >> +Vdd ----/\/\
o o
o---Vss common
> >> |
> >> 1k |
> >> P0 ----o----/\/\
o
> >> | |
> >> ===== 0.1 debounce |
> >> | |
> >> `
'
> > >
> >> -- regards,
> >> Tracy Allen
> >> electronically monitored ecosystems
> >> mailto:tracy@e...
> > > http://www.emesystems.com
> >>
> >
>coming from the prox switch. Power, ground, and the load, where do I
>put the resistor and the capacitor.
Okay, it is not a reed relay. What part number is the prox switch?
Does it need a pull-up or pull-down resistor?
sensor.
If it is....
They usually come in four variants - PNP & NPN
....and Normally Open or Normally Closed.
On an NPN you put the load between load and power.
PNP types between load and ground.
How many volts are you applying to its power
lead?. The ones I use (for wheel speed sensing
take between 10 & 35 volts DC). They work down to
8(ish) volts, but no lower.
Hope that helps
Les Otter
>
Original Message
> From: Tracy Allen [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=PVbX1ytg2vfEyJEU6u434kRnN5gzImUAFW9D8HlQVri7x3ChaE6qu26orlmLHmdENryeMOKmVeQaviFosew]tracy@e...[/url
> Sent: 08 March 2002 21:58
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Re: Proximity
> Switch and count Function
>
>
> >Hi Tracy, I am not understanding your
> schematic. I have three leads
> >coming from the prox switch. Power,
> ground, and the load, where do I
> >put the resistor and the capacitor.
>
>
> Okay, it is not a reed relay. What
> part number is the prox switch?
> Does it need a pull-up or pull-down resistor?
>
>
>
>
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>
> >Hi Tracy, I am not understanding your schematic. I have three
leads
> >coming from the prox switch. Power, ground, and the load, where do
I
> >put the resistor and the capacitor.
>
>
> Okay, it is not a reed relay. What part number is the prox switch?
> Does it need a pull-up or pull-down resistor?
Tracy, I am using a Allen bradley Prox # 871C-D2NP8 - E2 A and
presently not using a pull-up pull-down resistor.
Loren
Normally, you should use a load resistor. The output device of the sensor is
often a transistor with an open collector connexion. You need to supply this
collector via a resistor. If it's a PNP output, you must connect a resistor
between output and negative side of the power supply. If it's a NPN, the
resistor must be between output and positive side of the power supply. If
you omit the resistor, the output is like floating, and the Stamp input is
not properly driven, giving erratic measures.
Best regards,
Phil.
> Tracy, I am using a Allen bradley Prox # 871C-D2NP8 - E2 A and
> presently not using a pull-up pull-down resistor.
>
> Loren
Thanks for the help.
Loren
--- In basicstamps@y..., "Derenne Philippe" <derennep@s...> wrote:
> Hi,
>
> Normally, you should use a load resistor. The output device of the
sensor is
> often a transistor with an open collector connexion. You need to
supply this
> collector via a resistor. If it's a PNP output, you must connect a
resistor
> between output and negative side of the power supply. If it's a
NPN, the
> resistor must be between output and positive side of the power
supply. If
> you omit the resistor, the output is like floating, and the Stamp
input is
> not properly driven, giving erratic measures.
>
> Best regards,
>
> Phil.
>
>
> > Tracy, I am using a Allen bradley Prox # 871C-D2NP8 - E2 A and
> > presently not using a pull-up pull-down resistor.
> >
> > Loren