Analog Switch question

  • Thread starter Michael Kennedy
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Michael Kennedy

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Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an AD7512
or something like that.


For example, I have a usb cable I will plug into a tablet. It needs to
short the D+ and D- pins (on the cable going to the tablet) together for
a couple of seconds then connect the the D+ and D- (from a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to a
hub all on one USB port.
 
On 3/4/2015 2:39 PM, Michael Kennedy wrote:
Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an AD7512
or something like that.


For example, I have a usb cable I will plug into a tablet. It needs to
short the D+ and D- pins (on the cable going to the tablet) together for
a couple of seconds then connect the the D+ and D- (from a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to a
hub all on one USB port.
Click to expand...

By the way, sorry if you see my message twice. I tried posting from a
google account to see if anyone would read it.

I just got a real Usenet provider again for the first time in years.
 
On 3/3/2015 11:39 PM, Michael Kennedy wrote:
Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an AD7512
or something like that.


For example, I have a usb cable I will plug into a tablet. It needs to
short the D+ and D- pins (on the cable going to the tablet) together for
a couple of seconds then connect the the D+ and D- (from a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to a
hub all on one USB port.
Click to expand...

Do you need it automatic, or can you just put a DPDT momentary switch
on it and be done?
Mikek

---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com
 
On 3/5/2015 3:15 AM, amdx wrote:
On 3/3/2015 11:39 PM, Michael Kennedy wrote:
Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an AD7512
or something like that.


For example, I have a usb cable I will plug into a tablet. It needs to
short the D+ and D- pins (on the cable going to the tablet) together for
a couple of seconds then connect the the D+ and D- (from a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to a
hub all on one USB port.

Do you need it automatic, or can you just put a DPDT momentary switch
on it and be done?
Mikek

---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com
Click to expand...

Well, I have it with a switch now and it works just fine.
That's how I know this works and made that circuit diagram.

A switch is a simple solution but I guess I was wanting to turn this
into a project I can learn something from.
This seems like it should be a fairly simple circuit to build.
but when it comes to designing circuits I have almost no experience
so I figured I'd ask around since I don't know what kind of devices are
out there.

Maybe I should post this over on s.e.design.
 
On 3/4/2015 6:36 PM, Michael Kennedy wrote:
On 3/5/2015 3:15 AM, amdx wrote:
On 3/3/2015 11:39 PM, Michael Kennedy wrote:
Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an AD7512
or something like that.


For example, I have a usb cable I will plug into a tablet. It needs to
short the D+ and D- pins (on the cable going to the tablet) together for
a couple of seconds then connect the the D+ and D- (from a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to a
hub all on one USB port.

Do you need it automatic, or can you just put a DPDT momentary switch
on it and be done?
Mikek

---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com


Well, I have it with a switch now and it works just fine.
That's how I know this works and made that circuit diagram.

A switch is a simple solution but I guess I was wanting to turn this
into a project I can learn something from.
This seems like it should be a fairly simple circuit to build.
but when it comes to designing circuits I have almost no experience
so I figured I'd ask around since I don't know what kind of devices are
out there.

Maybe I should post this over on s.e.design.

I was thinking about a 555 and some kind of analog switch like an
AD7512
Click to expand...

What are you planing on using as the trigger for the 555?
Just the power from when the USB is plugged into the tablet.
hmm I think there is already voltage on the power pins
What are the other uses of the USB.
If you put the circuit internal to the tablet will this affect those
other devices.
You could switch a small DPDT relay with the 555.
Mikek
 
"Michael Kennedy" <mike...@crap.comcast.net> wrote in message
news:md65od$807$1@dont-email.me...
Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an AD7512
or something like that.


For example, I have a usb cable I will plug into a tablet. It needs to
short the D+ and D- pins (on the cable going to the tablet) together for a
couple of seconds then connect the the D+ and D- (from a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to a
hub all on one USB port.
Click to expand...

How about just keeping it really simple ? All you need is a small DPDT relay
with a high sensitivity 5v coil (Mouser, Digikey etc) , and an electrolytic
cap of a few tens of uF.

Just wire +5v -> Relay coil -> cap -> GND. When you plug in, the cap
will charge via the relay coil. The charging current through the coil will
pull the relay. As the cap approaches full charge, the current through the
coil will drop close to zero, and the relay will drop back out. The length
of time that the relay stays closed for will depend on the DC resistance of
the coil, the relay sensitivity, and the value of the cap. The whole thing
could be 'tidied up' a bit if the operation of the relay is a bit 'scruffy',
by adding an NPN transistor and a resistor to the mix. In that case, it
would be +5v -> R -> C -> GND

Then from the junction of R and C you would take a connection to the base
of the transistor. The remainder of the circuit would be +5v -> Relay
coil -> Tr collector // Tr emitter -> GND.

You would need to have a diode connected directly across the relay coil,
cathode to 5v anode to transistor collector. This is to protect the
transistor from reverse spikes from the coil when it is de-energised. The
value of the resistor needs to be between about 2k and 47k. The time delay
will be in the vicinity of 0.7 CR. 22k and 68uF would be a couple of good
values to start with. With this driver transistor added, the relay can be
pretty much anything with a 5v coil that comes to hand. No need for it to be
a high sensitivity type.

There are other little sophistications that could be added in as well, such
as a diode across the charging R. That will ensure that when you unplug, and
the 5v disappears, the diode becomes forward biased by the charge on the
cap, dumping that charge into the rail, ensuring that the cap is quickly
discharged so that the timing will work again if you plug straight back in.

These are just ideas based on generic circuit elements, but some combination
of them should work for you. You could of course go down the 555 timer
route, but that seems needlessly complicated to me.

Arfa
 
On 3/5/2015 6:08 PM, Arfa Daily wrote:
"Michael Kennedy" <mike...@crap.comcast.net> wrote in message
news:md65od$807$1@dont-email.me...
Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an
AD7512 or something like that.


For example, I have a usb cable I will plug into a tablet. It needs
to short the D+ and D- pins (on the cable going to the tablet)
together for a couple of seconds then connect the the D+ and D- (from
a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to
a hub all on one USB port.


How about just keeping it really simple ? All you need is a small DPDT
relay with a high sensitivity 5v coil (Mouser, Digikey etc) , and an
electrolytic cap of a few tens of uF.

Just wire +5v -> Relay coil -> cap -> GND. When you plug in, the
cap will charge via the relay coil. The charging current through the
coil will pull the relay. As the cap approaches full charge, the current
through the coil will drop close to zero, and the relay will drop back
out. The length of time that the relay stays closed for will depend on
the DC resistance of the coil, the relay sensitivity, and the value of
the cap. The whole thing could be 'tidied up' a bit if the operation of
the relay is a bit 'scruffy', by adding an NPN transistor and a resistor
to the mix. In that case, it would be +5v -> R -> C -> GND

Then from the junction of R and C you would take a connection to the
base of the transistor. The remainder of the circuit would be +5v
-> Relay coil -> Tr collector // Tr emitter -> GND.

You would need to have a diode connected directly across the relay coil,
cathode to 5v anode to transistor collector. This is to protect the
transistor from reverse spikes from the coil when it is de-energised.
The value of the resistor needs to be between about 2k and 47k. The time
delay will be in the vicinity of 0.7 CR. 22k and 68uF would be a
couple of good values to start with. With this driver transistor added,
the relay can be pretty much anything with a 5v coil that comes to hand.
No need for it to be a high sensitivity type.

There are other little sophistications that could be added in as well,
such as a diode across the charging R. That will ensure that when you
unplug, and the 5v disappears, the diode becomes forward biased by the
charge on the cap, dumping that charge into the rail, ensuring that the
cap is quickly discharged so that the timing will work again if you plug
straight back in.

These are just ideas based on generic circuit elements, but some
combination of them should work for you. You could of course go down the
555 timer route, but that seems needlessly complicated to me.

Arfa
Click to expand...
How about a pushbutton switch on the connector you plug in?
Not everything in the world requires an electronic solution.
 
On 3/5/2015 8:08 PM, Arfa Daily wrote:
"Michael Kennedy" <mike...@crap.comcast.net> wrote in message
news:md65od$807$1@dont-email.me...
Looking for some advice on how to make this.

I need to make a DTDP analog switch work with a few second delay after
receiving input.

I was thinking about a 555 and some kind of analog switch like an
AD7512 or something like that.


For example, I have a usb cable I will plug into a tablet. It needs
to short the D+ and D- pins (on the cable going to the tablet)
together for a couple of seconds then connect the the D+ and D- (from
a usb hub).


You can read my description below or look at the circuit I drew here.

http://tinypic.com/r/3326wpf/8

The hub will provide power to charge the tablet, but to put the tablet
into charge mode you need to short the pins first. After that you can
disconnect the short and it will continue charging. Switch in the USB
hub's data lines and everything is working. Charging and connected to
a hub all on one USB port.


How about just keeping it really simple ? All you need is a small DPDT
relay with a high sensitivity 5v coil (Mouser, Digikey etc) , and an
electrolytic cap of a few tens of uF.

Just wire +5v -> Relay coil -> cap -> GND. When you plug in, the
cap will charge via the relay coil. The charging current through the
coil will pull the relay. As the cap approaches full charge, the current
through the coil will drop close to zero, and the relay will drop back
out. The length of time that the relay stays closed for will depend on
the DC resistance of the coil, the relay sensitivity, and the value of
the cap. The whole thing could be 'tidied up' a bit if the operation of
the relay is a bit 'scruffy', by adding an NPN transistor and a resistor
to the mix. In that case, it would be +5v -> R -> C -> GND

Then from the junction of R and C you would take a connection to the
base of the transistor. The remainder of the circuit would be +5v
-> Relay coil -> Tr collector // Tr emitter -> GND.

You would need to have a diode connected directly across the relay coil,
cathode to 5v anode to transistor collector. This is to protect the
transistor from reverse spikes from the coil when it is de-energised.
The value of the resistor needs to be between about 2k and 47k. The time
delay will be in the vicinity of 0.7 CR. 22k and 68uF would be a
couple of good values to start with. With this driver transistor added,
the relay can be pretty much anything with a 5v coil that comes to hand.
No need for it to be a high sensitivity type.

There are other little sophistications that could be added in as well,
such as a diode across the charging R. That will ensure that when you
unplug, and the 5v disappears, the diode becomes forward biased by the
charge on the cap, dumping that charge into the rail, ensuring that the
cap is quickly discharged so that the timing will work again if you plug
straight back in.

These are just ideas based on generic circuit elements, but some
combination of them should work for you. You could of course go down the
555 timer route, but that seems needlessly complicated to me.

Arfa
Click to expand...

I like it, and mad that I didn't think of it!
Mikek
 
Arfa
How about a pushbutton switch on the connector you plug in?
Not everything in the world requires an electronic solution.
Click to expand...

If you read all of the posts, that was already suggested to the OP, and he
says that is how he does it now and it works well enough, but he wants to do
it automatically with a bit of electronics, as much as an exercise in
designing and understanding some simple circuitry, as producing the
functionality ...

Arfa
 
These are just ideas based on generic circuit elements, but some
combination of them should work for you. You could of course go down the
555 timer route, but that seems needlessly complicated to me.

Arfa

I like it, and mad that I didn't think of it!
Mikek
Click to expand...

Why thank you, kind sir ... ! d:)

Arfa
 
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