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design | Pulsing DC Signal Relay Control...
There are 19 messages in this thread.
You are currently looking at messages 0 to 10.
Pulsing DC Signal Relay Control... - 2008-06-10 11:43:00
Hello, I am trying to construct a relay control circuit based on an input waveform. The waveform can take on two states - a 0 --> 14.4V DC square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: http://img87.imageshack.us/img87/8307/drlpwmep8.png With the squarewave as input, the relay is to be in one state, with the constant DC, the relay is to be in the opposite state. I have tried two approaches from an original post here: http://groups.google.com/group/sci.electronics.design/browse_thread/thread/fabadb68f86a3902/53c5787e0879df60?lnk=gst& ;q=ac+choke#53c5787e0879df60 Including using a MOSFET with cap and 2 resistors and a circuit with a large cap, resistor and diode, but they seem to produce intermittent results. The key factors are: 1) Simple circuit - as few parts as possible 2) Large caps (up to 10,000uF) and high wattage resistors are OK 3) Able to utilize relays with different characteristics (i.e. different coil resistances) Someone on the original post mentioned a "monopulser", but I cannot find information on that anywhere. This sounds ideal though - something that keeps the input high (or low) when pulses exist and then flips states when the pulses disappear... TIA
Re: Pulsing DC Signal Relay Control... - Fred Bloggs - 2008-06-10 12:01:00
> > I am trying to construct a relay control circuit based on an input > waveform. The waveform can take on two states - a 0 --> 14.4V DC > square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: > > http://img87.imageshack.us/img87/8307/drlpwmep8.png > > With the squarewave as input, the relay is to be in one state, with > the constant DC, the relay is to be in the opposite state. > > I have tried two approaches from an original post here: > > http://groups.google.com/group/sci.electronics.design/browse_thread/thread/fabadb68f86a3902/53c5787e0879df60?lnk=gst& ;q=ac+choke#53c5787e0879df60 > > Including using a MOSFET with cap and 2 resistors and a circuit with a > large cap, resistor and diode, but they seem to produce intermittent > results. > > The key factors are: > > 1) Simple circuit - as few parts as possible > 2) Large caps (up to 10,000uF) and high wattage resistors are OK > 3) Able to utilize relays with different characteristics (i.e. > different coil resistances) > > Someone on the original post mentioned a "monopulser", but I cannot > find information on that anywhere. This sounds ideal though - > something that keeps the input high (or low) when pulses exist and > then flips states when the pulses disappear... I recall that idiot question and told you at that time to go with a double pole switch. If you have a problem with that then tell us what it is....
Re: Pulsing DC Signal Relay Control... - Jan Panteltje - 2008-06-10 12:01:00
On a sunny day (Tue, 10 Jun 2008 08:43:55 -0700 (PDT)) it happened a...@hotmail.com wrote in <3...@56g2000hsm.googlegroups.com>: >Hello, > >I am trying to construct a relay control circuit based on an input >waveform. The waveform can take on two states - a 0 --> 14.4V DC >square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: >The key factors are: > >1) Simple circuit - as few parts as possible >2) Large caps (up to 10,000uF) and high wattage resistors are OK >3) Able to utilize relays with different characteristics (i.e. >different coil resistances) So we only bring it up with AC: + - A B input ---------- C1-------- k diode a ---------------- | | | a | - | diode C2 relay k | + | | | | /// /// /// In case of a 0 --> 14.4V DC square wave at the input: In A is a 14.4V square wave, from + 0.7 to - 13.7 V. In B is a - 13 V DC voltage. In case of + DC on the input: There is undefined in A and nothing in B. The electrolytic capacitors can be the same value, perhaps 25V volatge rating. The value depends on the relay current, so on the relay coil resistance. For 55 Hz, say less then 20mS and relay colil resistance of R, think RC time for discharge to a level before where the relais drops off. Maybe 4700uF is enough....
Re: Pulsing DC Signal Relay Control... - Bob Eld - 2008-06-10 12:16:00
<a...@hotmail.com> wrote in message news:3...@56g2000hsm.googlegroups.com... > Hello, > > I am trying to construct a relay control circuit based on an input > waveform. The waveform can take on two states - a 0 --> 14.4V DC > square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: > > http://img87.imageshack.us/img87/8307/drlpwmep8.png > > With the squarewave as input, the relay is to be in one state, with > the constant DC, the relay is to be in the opposite state. > > I have tried two approaches from an original post here: > > http://groups.google.com/group/sci.electronics.design/browse_thread/thread/f abadb68f86a3902/53c5787e0879df60?lnk=gst&q=ac+choke#53c5787e0879df60 > > Including using a MOSFET with cap and 2 resistors and a circuit with a > large cap, resistor and diode, but they seem to produce intermittent > results. > > The key factors are: > > 1) Simple circuit - as few parts as possible > 2) Large caps (up to 10,000uF) and high wattage resistors are OK > 3) Able to utilize relays with different characteristics (i.e. > different coil resistances) > > Someone on the original post mentioned a "monopulser", but I cannot > find information on that anywhere. This sounds ideal though - > something that keeps the input high (or low) when pulses exist and > then flips states when the pulses disappear... > > TIA Simple: Two caps and two diodes. Make a voltage doubler, one cap C1 in series with the source connected to a forward diode, D1, anode. Second diode, D2 anode to ground, cathode to anode of D1. Cathode of D1 to cap, C2, and to relay coil. Ground other end of C2 and other end of relay coil. State 1. AC wave form is rectified to peak value of waveform, 14.4 volts minus losses. This voltage pulls in the relay. State 2. Straight DC won't go through C1, so relay remains unenergized. Cap size depends on the relay current required. Relay voltage = 12 Volts.
Re: Pulsing DC Signal Relay Control... - Jamie - 2008-06-10 19:20:00
Jan Panteltje wrote: > On a sunny day (Tue, 10 Jun 2008 08:43:55 -0700 (PDT)) it happened > a...@hotmail.com wrote in > <3...@56g2000hsm.googlegroups.com>: > > >>Hello, >> >>I am trying to construct a relay control circuit based on an input >>waveform. The waveform can take on two states - a 0 --> 14.4V DC >>square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: > > >>The key factors are: >> >>1) Simple circuit - as few parts as possible >>2) Large caps (up to 10,000uF) and high wattage resistors are OK >>3) Able to utilize relays with different characteristics (i.e. >>different coil resistances) > > > So we only bring it up with AC: > > > > + - A B > input ---------- C1-------- k diode a ---------------- > | | | > a | - | > diode C2 relay > k | + | > | | | > /// /// /// > > > In case of a 0 --> 14.4V DC square wave at the input: > In A is a 14.4V square wave, from + 0.7 to - 13.7 V. > In B is a - 13 V DC voltage. > > In case of + DC on the input: > There is undefined in A and nothing in B. > > The electrolytic capacitors can be the same value, > perhaps 25V volatge rating. > The value depends on the relay current, so on the relay coil resistance. > For 55 Hz, say less then 20mS and relay colil resistance of R, > think RC time for discharge to a level before where the relais drops off. > > Maybe 4700uF is enough.... > I guess that would work real fine and dandy how ever, while your at it did you ever stop and think that maybe he's deriving that signal from a low current source ? In which case since you want to slop it out, a totem pole output trannies as a unity gain stage to drive this little radio shack of a kit idea circuit!. or Maybe, a driving transistor for the coil! http://webpages.charter.net/jamie_5";
Re: Pulsing DC Signal Relay Control... - Hammy - 2008-06-10 19:28:00
On Tue, 10 Jun 2008 08:43:55 -0700 (PDT), a...@hotmail.com wrote: >something that keeps the input high (or low) when pulses exist and >then flips states when the pulses disappear... > >TIA Maybe something like this may be useful for that function. D-Type Transparent Latch http://rocky.digikey.com/weblib/ST%20Micro/Web%20Data/74V1T77.pdf
Re: Pulsing DC Signal Relay Control... - John Fields - 2008-06-10 22:39:00
On Tue, 10 Jun 2008 08:43:55 -0700 (PDT), a...@hotmail.com wrote: >Hello, > >I am trying to construct a relay control circuit based on an input >waveform. The waveform can take on two states - a 0 --> 14.4V DC >square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: > >http://img87.imageshack.us/img87/8307/drlpwmep8.png > >With the squarewave as input, the relay is to be in one state, with >the constant DC, the relay is to be in the opposite state. > >I have tried two approaches from an original post here: > >http://groups.google.com/group/sci.electronics.design/browse_thread/thread/fabadb68f86a3902/53c5787e0879df60?lnk=gst &q=ac+choke#53c5787e0879df60 > >Including using a MOSFET with cap and 2 resistors and a circuit with a >large cap, resistor and diode, but they seem to produce intermittent >results. > >The key factors are: > >1) Simple circuit - as few parts as possible >2) Large caps (up to 10,000uF) and high wattage resistors are OK >3) Able to utilize relays with different characteristics (i.e. >different coil resistances) > >Someone on the original post mentioned a "monopulser", but I cannot >find information on that anywhere. This sounds ideal though - >something that keeps the input high (or low) when pulses exist and >then flips states when the pulses disappear... --- What you need is simply a retriggerable monostable multivibrator: V+>------------------------------------+ | +-->RELAY COIL K| Vcc>--------------+-------+ [DIODE] | | | [Rt] | +-->RELAY COIL | +--+--+ | VIN---[R1]--+-----|----|T | D | | | OUT|--[R]--G N | +----|RC | S [R2] | +--+--+ | | [Ct] | | | | | | GND---------+-----+-------+------------+ And you adjust the values of Rt and Ct so that the output pulse from the one-shot: lasts for somewhat longer than the period of the 55Hz signal, like this: |<--11.8ms-->|<-6.4ms-> ____________ ____________ ____________ VIN___| |_________| |_________| ___________________________ OUT___| |______________________________ In reality what will happen is that the one-shot's output will be extended for an additional RtCt time if it's high when VIN goes high and it'll stay high as long as VIN continues to toggle, like this: ____________ ____________ ____________ VIN___| |_________| |_________| __________________________________________________________ OUT___| However, when VIN _stays_ high, the one-shot will time out and OUT will go low, turning off the relay: ____________ ___________________________________ VIN___| |_________| _________________________________________________ OUT___| |________ R1 and R2 are a voltage divider used to cut VIN down to something the one-shot wants to see, around 4V when VIN is high. A good choice for the one shot would be either an HC123 or an HC4538. JF
Re: Pulsing DC Signal Relay Control... - John Fields - 2008-06-10 22:50:00
On Tue, 10 Jun 2008 21:39:43 -0500, John Fields <j...@austininstruments.com> wrote: >On Tue, 10 Jun 2008 08:43:55 -0700 (PDT), a...@hotmail.com wrote: > >>Hello, >> >>I am trying to construct a relay control circuit based on an input >>waveform. The waveform can take on two states - a 0 --> 14.4V DC >>square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: >> >>http://img87.imageshack.us/img87/8307/drlpwmep8.png >> >>With the squarewave as input, the relay is to be in one state, with >>the constant DC, the relay is to be in the opposite state. >> >>I have tried two approaches from an original post here: >> >>http://groups.google.com/group/sci.electronics.design/browse_thread/thread/fabadb68f86a3902/53c5787e0879df60?lnk =gst&q=ac+choke#53c5787e0879df60 >> >>Including using a MOSFET with cap and 2 resistors and a circuit with a >>large cap, resistor and diode, but they seem to produce intermittent >>results. >> >>The key factors are: >> >>1) Simple circuit - as few parts as possible >>2) Large caps (up to 10,000uF) and high wattage resistors are OK >>3) Able to utilize relays with different characteristics (i.e. >>different coil resistances) >> >>Someone on the original post mentioned a "monopulser", but I cannot >>find information on that anywhere. This sounds ideal though - >>something that keeps the input high (or low) when pulses exist and >>then flips states when the pulses disappear... > >--- >What you need is simply a retriggerable monostable multivibrator: > >V+>------------------------------------+ > | > +-->RELAY COIL > K| >Vcc>--------------+-------+ [DIODE] > | | | > [Rt] | +-->RELAY COIL > | +--+--+ | >VIN---[R1]--+-----|----|T | D > | | | OUT|--[R]--G N > | +----|RC | S > [R2] | +--+--+ | > | [Ct] | | > | | | | >GND---------+-----+-------+------------+ > >And you adjust the values of Rt and Ct so that the output pulse from >the one-shot: lasts for somewhat longer than the period of the 55Hz >signal, like this: > > |<--11.8ms-->|<-6.4ms-> > ____________ ____________ ____________ >VIN___| |_________| |_________| > > ___________________________ >OUT___| |______________________________ > >In reality what will happen is that the one-shot's output will be >extended for an additional RtCt time if it's high when VIN goes high >and it'll stay high as long as VIN continues to toggle, like this: > > ____________ ____________ ____________ >VIN___| |_________| |_________| > > __________________________________________________________ >OUT___| > > >However, when VIN _stays_ high, the one-shot will time out and OUT >will go low, turning off the relay: > > ____________ ___________________________________ >VIN___| |_________| > > _________________________________________________ >OUT___| |________ --- One caveat: note that relay will close for one RC time when VIN goes high and stays high: _________________________________________________________ VIN___| ___________________________ OUT___| |______________________________ If that's going to be a problem for you it can be fixed by "ignoring" the first edge, but at the cost of an ON delay one RC wide. I think... JF
Re: Pulsing DC Signal Relay Control... - Fred Bloggs - 2008-06-11 06:48:00
John Fields wrote: > On Tue, 10 Jun 2008 21:39:43 -0500, John Fields > <j...@austininstruments.com> wrote: > > >>On Tue, 10 Jun 2008 08:43:55 -0700 (PDT), a...@hotmail.com wrote: >> >> >>>Hello, >>> >>>I am trying to construct a relay control circuit based on an input >>>waveform. The waveform can take on two states - a 0 --> 14.4V DC >>>square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC: >>> >>>http://img87.imageshack.us/img87/8307/drlpwmep8.png >>> >>>With the squarewave as input, the relay is to be in one state, with >>>the constant DC, the relay is to be in the opposite state. >>> >>>I have tried two approaches from an original post here: >>> >>>http://groups.google.com/group/sci.electronics.design/browse_thread/thread/fabadb68f86a3902/53c5787e0879df60 ?lnk=gst&q=ac+choke#53c5787e0879df60 >>> >>>Including using a MOSFET with cap and 2 resistors and a circuit with a >>>large cap, resistor and diode, but they seem to produce intermittent >>>results. >>> >>>The key factors are: >>> >>>1) Simple circuit - as few parts as possible >>>2) Large caps (up to 10,000uF) and high wattage resistors are OK >>>3) Able to utilize relays with different characteristics (i.e. >>>different coil resistances) >>> >>>Someone on the original post mentioned a "monopulser", but I cannot >>>find information on that anywhere. This sounds ideal though - >>>something that keeps the input high (or low) when pulses exist and >>>then flips states when the pulses disappear... >> >>--- >>What you need is simply a retriggerable monostable multivibrator: >> >>V+>------------------------------------+ >> | >> +-->RELAY COIL >> K| >>Vcc>--------------+-------+ [DIODE] >> | | | >> [Rt] | +-->RELAY COIL >> | +--+--+ | >>VIN---[R1]--+-----|----|T | D >> | | | OUT|--[R]--G N >> | +----|RC | S >> [R2] | +--+--+ | >> | [Ct] | | >> | | | | >>GND---------+-----+-------+------------+ >> >>And you adjust the values of Rt and Ct so that the output pulse from >>the one-shot: lasts for somewhat longer than the period of the 55Hz >>signal, like this: >> >> |<--11.8ms-->|<-6.4ms-> >> ____________ ____________ ____________ >>VIN___| |_________| |_________| >> >> ___________________________ >>OUT___| |______________________________ >> >>In reality what will happen is that the one-shot's output will be >>extended for an additional RtCt time if it's high when VIN goes high >>and it'll stay high as long as VIN continues to toggle, like this: >> >> ____________ ____________ ____________ >>VIN___| |_________| |_________| >> >> __________________________________________________________ >>OUT___| >> >> >>However, when VIN _stays_ high, the one-shot will time out and OUT >>will go low, turning off the relay: >> >> ____________ ___________________________________ >>VIN___| |_________| >> >> _________________________________________________ >>OUT___| |________ > > > > --- > One caveat: note that relay will close for one RC time when VIN goes > high and stays high: > > _________________________________________________________ > VIN___| > > ___________________________ > OUT___| |______________________________ > > If that's going to be a problem for you it can be fixed by "ignoring" > the first edge, but at the cost of an ON delay one RC wide. > > I think... > > > JF He can trigger on the negative going edge ....
Re: Pulsing DC Signal Relay Control... - 2008-06-11 07:12:00
On 11 jun, 01:22, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> Jan Panteltje wrote:
> > On a sunny day (Tue, 10 Jun 2008 08:43:55 -0700 (PDT)) it happened
> > afeud...@hotmail.com wrote in
> > <3917ab0e-f7b6-4c9a-ba29-6c93e6126...@56g2000hsm.googlegroups.com>:
>
> >>Hello,
>
> >>I am trying to construct a relay control circuit based on an input
> >>waveform. The waveform can take on two states - a 0 --> 14.4V DC
> >>square wave at 55Hz and 65% duty cycle OR a constant 14.4V DC:
>
> >>The key factors are:
>
> >>1) Simple circuit - as few parts as possible
> >>2) Large caps (up to 10,000uF) and high wattage resistors are OK
> >>3) Able to utilize relays with different characteristics (i.e.
> >>different coil resistances)
>
> > So we only bring it up with AC:
>
> > + - A B
> > input ---------- C1-------- k diode a ----------------
> > | | |
> > a | - |
> > diode C2 relay
> > k | + |
> > | | |
> > /// /// ///
>
> > In case of a 0 --> 14.4V DC square wave at the input:
> > In A is a 14.4V square wave, from + 0.7 to - 13.7 V.
> > In B is a - 13 V DC voltage.
>
> > In case of + DC on the input:
> > There is undefined in A and nothing in B.
>
> > The electrolytic capacitors can be the same value,
> > perhaps 25V volatge rating.
> > The value depends on the relay current, so on the relay coil resistance.
> > For 55 Hz, say less then 20mS and relay colil resistance of R,
> > think RC time for discharge to a level before where the relais drops off.
>
> > Maybe 4700uF is enough....
>
> I guess that would work real fine and dandy how ever, while your at it
> did you ever stop and think that maybe he's deriving that signal from a
> low current source ?
> In which case since you want to slop it out, a totem pole
> output trannies as a unity gain stage to drive this little
> radio shack of a kit idea circuit!.
> or Maybe, a driving transistor for the coil!
In case of high impedance for the source, how about this:
input ----------------- R ------------------- 7,2V if AC, 14.4V if
DC ----------- +
| +10V -
opamp --- R - driver transistor with diode.
C
|
///
R can be very high, and C maybe 1uF, no need for large caps.