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Stretch 0.5sec pulse to 6sec

Started by amdx February 2, 2013
I have a 4 volt pulse that is 0.5 sec long.
I need a 6 sec pulse that will switch a 2n3904.
The 4 volts has about a 400 ohm source impedance.

  I could use a 555, but first I need to invert the signal then
drive my 2n3904 switch, so I have 2 transistors and a 555. Oh yes I 
could probably differentiate the 0.5 sec pulse to trigger the 555, so 
maybe only 1 transistor and a 555.

  Could someone help with a pulse stretcher circuit.
Maybe an RC, transistor, or, I have some FETs, J301 or 2N3819, probably 
a diode. That will drive my final 2N3904 switch.
   The 2N3904 switch is across the alert button on a Walkie Talkie and 
shorts about 3.5v to ground.


The longer story;
  This started with "Have 5v regulator need 9 volts"
That particular problem is solved. everything has good clean power.

I have a Harbor Freight *Driveway sensor.
The sensor triggers a receiver with RF.
The receiver in turn triggers the alert button on a **Walkie Talkie.
After a temporary install, I noted the Talkie alert signaled 10 times.
  That is to much, three times is fine.
  After trying several things to eliminate the 10 alerts, I finally 
wrapped the walkie talkie in aluminum foil. Problem solved. I'll deal 
with this later by putting the Harbor Freight receiver inside my boat 
and the walkie talkie outside where it's RF can get out. (it's an all 
Aluminum boat)
The 0.5 sec pulse causes one alert signal. A six second pulse causes 
three alert signals. Perfect!


*
http://www.harborfreight.com/wireless-driveway-alert-system-93068.html

** 
http://www.motorola.com/Business/US-EN/Business+Product+and+Services/Two-Way+Radios+-+Consumers/Talkabout+FV300+Two-Way+Radio_B2B_US_EN

            Mikek
On Sat, 02 Feb 2013 17:21:40 -0600, amdx <amdx@knologynotthis.net>
wrote:

>I have a 4 volt pulse that is 0.5 sec long.
Positive-going?
>I need a 6 sec pulse that will switch a 2n3904.
I presume, then, also positive-going?
>The 4 volts has about a 400 ohm source impedance. > > I could use a 555, but first I need to invert the signal then >drive my 2n3904 switch, so I have 2 transistors and a 555. Oh yes I >could probably differentiate the 0.5 sec pulse to trigger the 555, so >maybe only 1 transistor and a 555. > > Could someone help with a pulse stretcher circuit. >Maybe an RC, transistor, or, I have some FETs, J301 or 2N3819, probably >a diode. That will drive my final 2N3904 switch. > The 2N3904 switch is across the alert button on a Walkie Talkie and >shorts about 3.5v to ground. > > >The longer story; > This started with "Have 5v regulator need 9 volts" >That particular problem is solved. everything has good clean power. > >I have a Harbor Freight *Driveway sensor. >The sensor triggers a receiver with RF. >The receiver in turn triggers the alert button on a **Walkie Talkie. >After a temporary install, I noted the Talkie alert signaled 10 times. > That is to much, three times is fine. > After trying several things to eliminate the 10 alerts, I finally >wrapped the walkie talkie in aluminum foil. Problem solved. I'll deal >with this later by putting the Harbor Freight receiver inside my boat >and the walkie talkie outside where it's RF can get out. (it's an all >Aluminum boat) >The 0.5 sec pulse causes one alert signal. A six second pulse causes >three alert signals. Perfect! > > >* >http://www.harborfreight.com/wireless-driveway-alert-system-93068.html > >** >http://www.motorola.com/Business/US-EN/Business+Product+and+Services/Two-Way+Radios+-+Consumers/Talkabout+FV300+Two-Way+Radio_B2B_US_EN > > Mikek
...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On 2/2/2013 7:10 PM, Jim Thompson wrote:
> On Sat, 02 Feb 2013 17:21:40 -0600, amdx <amdx@knologynotthis.net> > wrote: > >> I have a 4 volt pulse that is 0.5 sec long. > > Positive-going? >
Yes.
>> I need a 6 sec pulse that will switch a 2n3904. > > I presume, then, also positive-going? >
You presume correctly. But you already new that. ;-) Mikek
On 2/2/2013 5:21 PM, amdx wrote:
> I have a 4 volt pulse that is 0.5 sec long. > I need a 6 sec pulse that will switch a 2n3904. > The 4 volts has about a 400 ohm source impedance. > > I could use a 555, but first I need to invert the signal then > drive my 2n3904 switch, so I have 2 transistors and a 555. Oh yes I > could probably differentiate the 0.5 sec pulse to trigger the 555, so > maybe only 1 transistor and a 555. > > Could someone help with a pulse stretcher circuit. > Maybe an RC, transistor, or, I have some FETs, J301 or 2N3819, probably > a diode. That will drive my final 2N3904 switch. > The 2N3904 switch is across the alert button on a Walkie Talkie and > shorts about 3.5v to ground. >
I have breadboarded the two transistor, 555 circuit. Three alert signals as wanted. I can wire it on a pcb in the morning, if no one comes up with a simple RC one transistor pulse stretcher. I couldn't make it work, maybe it can't be done. Seems the timing would be difficult, but for my circuit 20% fluctuation would be ok. Mikek
On 2013-02-02, amdx <amdx@knologynotthis.net> wrote:
> I have a 4 volt pulse that is 0.5 sec long. > I need a 6 sec pulse that will switch a 2n3904. > The 4 volts has about a 400 ohm source impedance. > > I could use a 555, but first I need to invert the signal then > drive my 2n3904 switch, so I have 2 transistors and a 555. Oh yes I > could probably differentiate the 0.5 sec pulse to trigger the 555, so > maybe only 1 transistor and a 555.
> Could someone help with a pulse stretcher circuit. > Maybe an RC, transistor, or, I have some FETs, J301 or 2N3819, probably > a diode. That will drive my final 2N3904 switch. > The 2N3904 switch is across the alert button on a Walkie Talkie and > shorts about 3.5v to ground.
you can't just use the discharge pin of the 555 instead of the collector of the 2n2904? is 200mA not enough? -- &#9858;&#9859; 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
amdx wrote:

> I have a 4 volt pulse that is 0.5 sec long. > I need a 6 sec pulse that will switch a 2n3904. > The 4 volts has about a 400 ohm source impedance. > > I could use a 555, but first I need to invert the signal then > drive my 2n3904 switch, so I have 2 transistors and a 555. Oh yes I > could probably differentiate the 0.5 sec pulse to trigger the 555, so > maybe only 1 transistor and a 555. > > Could someone help with a pulse stretcher circuit. > Maybe an RC, transistor, or, I have some FETs, J301 or 2N3819, probably > a diode. That will drive my final 2N3904 switch. > The 2N3904 switch is across the alert button on a Walkie Talkie and > shorts about 3.5v to ground. > > > The longer story; > This started with "Have 5v regulator need 9 volts" > That particular problem is solved. everything has good clean power. > > I have a Harbor Freight *Driveway sensor. > The sensor triggers a receiver with RF. > The receiver in turn triggers the alert button on a **Walkie Talkie. > After a temporary install, I noted the Talkie alert signaled 10 times. > That is to much, three times is fine. > After trying several things to eliminate the 10 alerts, I finally > wrapped the walkie talkie in aluminum foil. Problem solved. I'll deal > with this later by putting the Harbor Freight receiver inside my boat > and the walkie talkie outside where it's RF can get out. (it's an all > Aluminum boat) > The 0.5 sec pulse causes one alert signal. A six second pulse causes > three alert signals. Perfect! > > > * > http://www.harborfreight.com/wireless-driveway-alert-system-93068.html > > ** > http://www.motorola.com/Business/US-EN/Business+Product+and+Services/Two-Way+Radios+-+Consumers/Talkabout+FV300+Two-Way+Radio_B2B_US_EN > > > Mikek
| === GND .-. | |1MEG PTT load (Radio) | | | 0.5s Pulse 1k '-' ||-+ ___ | ||<- -|___|-->|+-------+-+-----------+-||-+ + | 1N914 + | --- 10uf === --- GND + | Power NMOS or what ever | === GND (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Depending on your Vgs(th) spec you use for the NMOS will determine the time off delay, which is what I think you're after. This is one should be ~ 5 to 6 secs. I didn't do a sim on this, just used a calculator but it should be close. THe pulse should pull the output down fast and the off delay will give you a slight ramp due to the way fets are biased and behave when the drain starts to get higher in voltage than the gate. This should work out. The diode is there to prevent back drain from the pulse source. Jamie
On 2/2/2013 7:38 PM, Jasen Betts wrote:
> On 2013-02-02, amdx <amdx@knologynotthis.net> wrote: >> I have a 4 volt pulse that is 0.5 sec long. >> I need a 6 sec pulse that will switch a 2n3904. >> The 4 volts has about a 400 ohm source impedance. >> >> I could use a 555, but first I need to invert the signal then >> drive my 2n3904 switch, so I have 2 transistors and a 555. Oh yes I >> could probably differentiate the 0.5 sec pulse to trigger the 555, so >> maybe only 1 transistor and a 555. > >> Could someone help with a pulse stretcher circuit. >> Maybe an RC, transistor, or, I have some FETs, J301 or 2N3819, probably >> a diode. That will drive my final 2N3904 switch. >> The 2N3904 switch is across the alert button on a Walkie Talkie and >> shorts about 3.5v to ground. > > you can't just use the discharge pin of the 555 instead of the collector of the > 2n2904? is 200mA not enough? > >
Do you mean the discharge (pin 2) or output (pin 3). The pin from the walkie talkie already has a voltage on it, pin 3 will source current to the walkie talkie before it sinks current. I need an open collector to pull the Walkie talkie low. That's my understanding for now. Mikek
amdx wrote:

> On 2/2/2013 7:38 PM, Jasen Betts wrote: > >> On 2013-02-02, amdx <amdx@knologynotthis.net> wrote: >> >>> I have a 4 volt pulse that is 0.5 sec long. >>> I need a 6 sec pulse that will switch a 2n3904. >>> The 4 volts has about a 400 ohm source impedance. >>> >>> I could use a 555, but first I need to invert the signal then >>> drive my 2n3904 switch, so I have 2 transistors and a 555. Oh yes I >>> could probably differentiate the 0.5 sec pulse to trigger the 555, so >>> maybe only 1 transistor and a 555. >> >> >>> Could someone help with a pulse stretcher circuit. >>> Maybe an RC, transistor, or, I have some FETs, J301 or 2N3819, probably >>> a diode. That will drive my final 2N3904 switch. >>> The 2N3904 switch is across the alert button on a Walkie Talkie and >>> shorts about 3.5v to ground. >> >> >> you can't just use the discharge pin of the 555 instead of the >> collector of the >> 2n2904? is 200mA not enough? >> >> > Do you mean the discharge (pin 2) or output (pin 3). > The pin from the walkie talkie already has a voltage on > it, pin 3 will source current to the walkie talkie before > it sinks current. I need an open collector to pull the Walkie talkie > low. That's my understanding for now. > Mikek >
if you drive the trigger input via the output of the timer through a R of lets say 100k for example. Connect a 50uf cap from the trigger input pin to common and then use a diode in parallel with the 100k R to quickly recharge the cap when the output is high. The anode of the diode will be on the output while the cathode is on the trigger input. WIth this configuration, you can drive the threshold pin from your 4 volt source for the TX PTT signal. This will force both the output pin to go low along with the discharge pin also going low. Take your pick which one you want to use. I would use the discharge pin since it is a open collector and not yet in use. The output pin will be busy discharging the cap so the trigger input will reset the output when it reaches 1/3 of the Vcc voltage. And that is another issue. Since you only have 4 volts to drive the threshold pin for the TX signal, your Vcc can not exceed 6 volts abs which is on the edge, I would use a common 5 volt post reg to be sure for the vcc. The diode that is placed there for quick reset can be tailored with adding a R in series with it if you don't want it respond to another input pulse too early.. THat is up to you. THis is just my opinion of course... others most likely have other ideas. Jamie
On 2/2/2013 8:42 PM, Jamie wrote:
> amdx wrote: > >> I have a 4 volt pulse that is 0.5 sec long. >> I need a 6 sec pulse that will switch a 2n3904. >> The 4 volts has about a 400 ohm source impedance. >> > > | > === > GND > .-. > | |1MEG PTT load (Radio) > | | | > 0.5s Pulse 1k '-' ||-+ > ___ | ||<- > -|___|-->|+-------+-+-----------+-||-+ > + | > 1N914 + | > --- 10uf === > --- GND > + > | Power NMOS or what ever > | > === > GND > (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) > > Depending on your Vgs(th) spec you use for the NMOS will determine > the time off delay, which is what I think you're after. > > This is one should be ~ 5 to 6 secs. > > I didn't do a sim on this, just used a calculator but it should be > close. > THe pulse should pull the output down fast and the off delay > will give you a slight ramp due to the way fets are biased and behave > when the drain starts to get higher in voltage than the gate. This > should work out. > > The diode is there to prevent back drain from the pulse source. > > Jamie > >
Thanks Jamie, That seems to be working well. I have it breadboarded using 500k and 47uf with an IRFBE30* MOSFET, because that's what I have. I'll work with it a bit more to get me centered between 2 alerts and 4 alerts. Right now it is alerting 3 times but I don't know if it is centered between 2 and 4 alerts. This will fit better in the case. Thanks again, Mikek Went back to the bench with a 1 meg pot, Found two alerts at 344k and 4 at 513k, centered at 428k and it consistently alerts 3 times. (47uf) * IRFBE30 800V 30amp 3 ohm on resistance. Overkill but I have it.
On Sun, 03 Feb 2013 11:02:01 -0600, amdx <amdx@knologynotthis.net>
wrote:

>On 2/2/2013 8:42 PM, Jamie wrote: >> amdx wrote: >> >>> I have a 4 volt pulse that is 0.5 sec long. >>> I need a 6 sec pulse that will switch a 2n3904. >>> The 4 volts has about a 400 ohm source impedance. >>> >> >> | >> === >> GND >> .-. >> | |1MEG PTT load (Radio) >> | | | >> 0.5s Pulse 1k '-' ||-+ >> ___ | ||<- >> -|___|-->|+-------+-+-----------+-||-+ >> + | >> 1N914 + | >> --- 10uf === >> --- GND >> + >> | Power NMOS or what ever >> | >> === >> GND >> (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) >> >> Depending on your Vgs(th) spec you use for the NMOS will determine >> the time off delay, which is what I think you're after. >> >> This is one should be ~ 5 to 6 secs. >> >> I didn't do a sim on this, just used a calculator but it should be >> close. >> THe pulse should pull the output down fast and the off delay >> will give you a slight ramp due to the way fets are biased and behave >> when the drain starts to get higher in voltage than the gate. This >> should work out. >> >> The diode is there to prevent back drain from the pulse source. >> >> Jamie >> >> > Thanks Jamie, > That seems to be working well. I have it breadboarded using 500k and >47uf with an IRFBE30* MOSFET, because that's what I have. > I'll work with it a bit more to get me centered between 2 alerts and 4 >alerts. Right now it is alerting 3 times but I don't know if it is >centered between 2 and 4 alerts. > This will fit better in the case. > Thanks again, Mikek > >Went back to the bench with a 1 meg pot, Found two alerts at 344k and 4 >at 513k, centered at 428k and it consistently alerts 3 times. (47uf) > > >* IRFBE30 800V 30amp 3 ohm on resistance. Overkill but I have it. >
Isn't a "Lert" some kind of bird ?>:-} ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.