Need Help with a 12 volt actuator circuit. I will use a remote to operate a 12 v actuator. The receiver has a wire that will accept up to -500mA of current when I push a button on my remote. That will be the trigger to trigger the circuit that will operate the actuator. I have a fairly good knowledge of electronics and various ICs but I tend to stay away from micro-controllers because I still need to learn the programing language.

I've attached a schematic. Please let me know if I 'm going in the right direction.
thankyou

 

Off the top the first 555 when the trigger button is pushed I don't think will trigger. To trigger a 555 as a one shot (monostable) the trigger pin 2 needs to go below 1/3 of Vcc. With 47K and 1 Meg from Vcc to Gnd I don't see the trigger getting below 1/3 of Vcc which would be around 2.66 volts.

Ron

 

The receiver has a wire that will accept up to -500mA of current

Do you mean it will sink 500mA? Is the "-" significant?

 

Off the top the first 555 when the trigger button is pushed I don't think will trigger. To trigger a 555 as a one shot (monostable) the trigger pin 2 needs to go below 1/3 of Vcc. With 47K and 1 Meg from Vcc to Gnd I don't see the trigger getting below 1/3 of Vcc which would be around 2.66 volts.

Ron

The top 555 timer operates in "delay on" mode automatically whenever power is first connected. It keep pin 4 low on the other 555 timer to prevent false triggering as the timing capacitor on the lower right 555 timer is charging.
The 2nd lower left 555 timer DO trigger after the button is pushed because for only a small fraction of a second, pin 2 sees 0 volts the moment the button is pushed as the capacitor is charging and then immediately rises to high to reset for another push of the button. When the button is release the 1 M ohm drain the capacitor to prepare it for another push. This is config this way to only allow one trigger per push independent of how long the user held the button down (another way to prevent this timer to output two pulses in one trigger of the button).
The 3rd lower right 555 timer is set to output the moment the 2nd 555 timer goes low. (Sequencing output via 555 timer - Taken from 555 timer datasheet sample circuit section)

 

Do you mean it will sink 500mA? Is the "-" significant?

yes Alec. It will sink -500 mA however this circuit will trigger with so little current that you can trigger it by just touching pin 2 on the 2nd lower left 555 timer with a piece of metal. So my receiver circuit that can sink 500mA is WAY OVERKILL to trigger this circuit.

thanks

 

OK guys. I've build this design on breadboard but there seems to be a problem. The circuit works fine for switching LEDs and non inductive loads but when I put my actuator in there, multiple pulses are emitted from the two lower 555 timer simultaneously. As a result the actuators oscillates. The Transistors trigger the relays which uses 20mA and the actuator uses 1.6A. Any Ideas?

 

Dont see why you need the first 555 holding the pins 4 low, you can use the 1uF cap and 1.5Meg resistor on the pins 4,that would hold pins 4 low for the intial delay, also i woul put a 100uF cap across the supply pins 1-8, of both the 555 timers, also a diode in series with the input of the voltage regulator to prevent pulses from the solenoid interruptimg the supply.

 

Why are you running the relay coils that drive the actuator off the regulated power supply?
Why not run them off 15V?
Why do you even need the relays?

Seems that the goal is to run the actuator out for about 1s, and then back in for about 1s. How do you keep the actuator from creeping?

 

I've build this design on breadboard but there seems to be a problem

That sounds familiar! . If your actuator current is passing through the same ground strip as your ICs use, this could interfere with their operation. You should be using a star ground system. Snubbers on the relay contacts would be advisable.

 

Off the top the first 555 when the trigger button is pushed I don't think will trigger. To trigger a 555 as a one shot (monostable) the trigger pin 2 needs to go below 1/3 of Vcc. With 47K and 1 Meg from Vcc to Gnd I don't see the trigger getting below 1/3 of Vcc which would be around 2.66 volts.

Ron

When I said "off the top" it was a figure of speach, not to mean the top 555. I understood that.

Ron

 

Tha

When I said "off the top" it was a figure of speach, not to mean the top 555. I understood that.

Ron

Thanks Ron, I understood what you meant too late. lol

 

Dont see why you need the first 555 holding the pins 4 low, you can use the 1uF cap and 1.5Meg resistor on the pins 4,that would hold pins 4 low for the intial delay, also i woul put a 100uF cap across the supply pins 1-8, of both the 555 timers, also a diode in series with the input of the voltage regulator to prevent pulses from the solenoid interruptimg the supply.

Thanks Dave. I don't understand how I can use the 1.5M ohm and the 1uf capacitor to create a 1 second delay on. I believe Pin 4 on the 555 timer is PNP transistor so for my application it must be low or grounded then return to high after 1 sec elapses. I think Even if a small voltage is applied on pin 4 it would still allow the 555 timer to miss fire when power is first introduced.

However I took your advise to put a diode on the input of the volt regulator and the decoupling capacitors on the ICs. Thanks

 

Why are you running the relay coils that drive the actuator off the regulated power supply?
Why not run them off 15V?
Why do you even need the relays?

Seems that the goal is to run the actuator out for about 1s, and then back in for about 1s. How do you keep the actuator from creeping?

Thanks for replying Mike. The voltage regulator is used to Supply clean power to the ICs and the Coils of the relay are rated at 6 Volts. The unregulated power comes from a 15-12 volt High capacity battery. I use the relays because I have a couple of 12-6 volts mini relays lying around and because the actuator uses 1.6A and 555 timer ICs can't provide that much current or the transistors that I currently have. I could also substitute the relays for High Current transistors but I don't think that won't solve my current problem. The actuator I'm using has a DC motor with Gears that is capable of pushing or pulling about 2kg or about 4 pounds.

 

That sounds familiar! . If your actuator current is passing through the same ground strip as your ICs use, this could interfere with their operation. You should be using a star ground system. Snubbers on the relay contacts would be advisable.

Thanks Alec . I will give your star grounding a try. What If I just used a diode on all the ground wire instead. Will that help with the ground looping?

 

Thanks Dave. I don't understand how I can use the 1.5M ohm and the 1uf capacitor to create a 1 second delay on. I believe Pin 4 on the 555 timer is PNP transistor so for my application it must be low or grounded then return to high after 1 sec elapses. I think Even if a small voltage is applied on pin 4 it would still allow the 555 timer to miss fire when power is first introduced.

However I took your advise to put a diode on the input of the volt regulator and the decoupling capacitors on the ICs. Thanks

Put your 1 uF capacitor to pin 4 and pin 1, and the 1.5Meg resistor from pin 4 to pin 8, this will hold pin 4 low for 1.5 seconds then the 555 will work.

the reason its retriggering when the solenoid is powered up is the supply isn't smoothing out the back Emf,

 

What If I just used a diode on all the ground wire instead. Will that help with the ground looping?

No, it won't . Google 'ground bounce'.

 

That sounds familiar! . If your actuator current is passing through the same ground strip as your ICs use, this could interfere with their operation. You should be using a star ground system. Snubbers on the relay contacts would be advisable.

Hey Alec, To my surprise, all my problems have been solved after I've install an RC Snubber across the actuator. No more oscillation. Is it really this significant? I still don't understand how the snubber could stop the actuator from oscillating.
Thanks again.

 

Good to hear the snubber works!

 

Because its suppressing the back emf, if it was just one way, you can use a diode, as its two way pulsing you need a snubber.