If both lower sections of the H-bridge were switched on at the same time that would provide the short circuit. If the released sides of the relay switching circuit driving the motor were connected that could also provide the short-circuiting function. BUT you must be careful to avoid accidentally short-circuiting the supply voltage. So the circuit arrangement will need some careful thinking. And now, after seeing the most recent posts, it seems that there could also have been a connections in the wiring issue.

The wiring is now correct (had to reverse two wires) and works based off of what sghioto showed me above and what you mentioned earlier about shorting the circuit. Thank you for your feedback..

 

Add wire as shown between NO contact of limit switches to the red wire from the Linear Actuator.
SG
View attachment 171587

Hi sghioto, Thanks again for the help. I wanted to circle back as the option you provided works for what I wanted to do and is working great. I wanted to ask is there a further way I can protect the relays from fusing down the line? I have seen the options of using diodes/resistors across the relay pins but I do not have access to the relays pins as they are already soldered onto the wireless control board and the bottom is glued to a mount. Is there a way to utilize diodes across the screw terminal connections on my setup? Thanks.

 

I wanted to ask is there a further way I can protect the relays from fusing down the line?

Do you know how much current the actuator draws?
SG

 

Do you know how much current the actuator draws?
SG

My current actuator provides 7000N Push/Pull force and under no load it draws 3.4Amp and under full load it pulls 11Amp.
I am however going to change that actuator to one that provides less push/pull force as the original one is so slow. The new one will provide 2500N Push/Pull force and under no load it draws 3.4Amp and under full load it pulls 26.4Amp I will never use either one under full force.

 

I think we can fix this,but...

1. Limit switch contact ratings have to be looked into. it's unlikely they can be rated for the motor current. Sometimes handling the relay coil current is difficult.
2. You need access to say +12 or ground and one relay should change state for UP and the other change state for down.

You can use two external automotive relays and limit switches that are rated for the relay coil current. A few diodes are sprinkled into the circuit too.

in any event, the external relays are initially wired so the common contact is to the motor and the NC contact is to a motor end.
The NO contact goes to +12. In the off state both sides of the motor are grounded, thus braked. If both activated, both sides are at _1\+12, thus braked. Either relay is either UP/Down.

When I have time, there is a greenhouse window thread on AAC that has a comprehensive control defined.

I'll explain the limit switch concept later. The limit switches prevent activation of a particular direction. They are wired NC and in series with each direction relay respectively.

 

KISS is correct, using the higher current actuator will probably exceed the current rating of the existing limit switches and contacts in the remote relay module. You use the contacts in the module and limit switches to control the auto relay coils.
SG

 

I got back, so here is my reference: https://forum.allaboutcircuits.com/...oof-window-control.134958/page-2#post-1131056

 

KISS is correct, using the higher current actuator will probably exceed the current rating of the existing limit switches and contacts in the remote relay module. You use the contacts in the module and limit switches to control the auto relay coils.
SG
View attachment 171911

Thanks. It makes sense. I will research this and see how this implements into my existing setup. What size diodes are you using in this diagram? Would they be 1N4001? How do you determine that.

 

I got back, so here is my reference: https://forum.allaboutcircuits.com/...oof-window-control.134958/page-2#post-1131056

Thanks.. I will research this.

 

Thanks. It makes sense. I will research this and see how this implements into my existing setup. What size diodes are you using in this diagram? Would they be 1N4001? How do you determine that.

PRV >2x the supply voltage. Current is minimal. Speed isn't important here. if it were a car, >200 V PRV minimum. A 1N4001 is fine.

Exceeding the PRV/PIV isn't destructive if the current is limited.

 

Have you considered putting the limit switch functions back at the H-bridge control side? That would allow using much smaller switches and thinner wires and possibly having tighter control. Most industrial systems put the limiting controls functions back at the control level instead of at the power drive part of the system. At least that was what our customers always demanded for production line machines. So that is something to consider at least.

 

Here https://www.mouser.com/datasheet/2/307/en-vx-16332.pdf is the datasheet for your limit switches. Note 100 mA @ 30V/

This http://www.farnell.com/datasheets/1490805.pdf datasheet puts the R of the coil at 96 ohms. 12/96= 125 mA which technically makes that uSwitch unsuitable.

 

which technically makes that uSwitch unsuitable.

Good catch KISS. I'm surprised they haven't already fused or opened up.
SG

 

The same gold contact low current switches could very well serve as pilot duty controls driving the H-bridge arrangement. I am thinking that you are using that to control the relays, but I may be wrong on that point. But no matter what, you can use the switches to control a single transistor relay driver if nothing else. A bit more complex, but it would simplify the power wiring a lot.

 

Good catch KISS. I'm surprised they haven't already fused or opened up.
SG

Your problem, in one form or another comes up quite frequently. The usual topic is automatic chicken coop doors,

I did the controls for a gantry crane for a model railroad for a company in the 1980's, so I had a little hands on experience with small motors and dynamic braking. No PWM, but dynamic braking and an H-bridges and one big motor with overrun issues. I did build a simple overcurrent crow-bar sort of think that set the voltage to 1.2V on an overload. A power cycle was necessary to reset.

I also built an automatic drapery closer in the same time frame for a balcony curtain for my GF.

 

Your problem, in one form or another comes up quite frequently. The usual topic is automatic chicken coop doors,

I did the controls for a gantry crane for a model railroad for a company in the 1980's, so I had a little hands on experience with small motors and dynamic braking. No PWM, but dynamic braking and an H-bridges and one big motor with overrun issues. I did build a simple overcurrent crow-bar sort of think that set the voltage to 1.2V on an overload. A power cycle was necessary to reset.

I also built an automatic drapery closer in the same time frame for a balcony curtain for my GF.

Thanks for all the help guys. I'm playing around with some of the suggested options to see what will work out for my project. Particularly looking into the Auto relay option integrated into my existing setup. That will probably work the best.

On another note I have another question. I have a store bought PWM Controlled 30A Dual Relay module configured as an H-bridge from another project to control a heave duty motor. It is controlled by an RC transmitter and receiver via a Futaba plug (black,red,white wires). I was wondering if there is a way to use my current wireless relay setup to be able to control this PWM relay module? I guess the real question is how do I create a PWM signal to control the PWM controlled relay without an RC transmitter and receiver. I'm wondering if I can use this somehow instead of the auto relays. Any ideas.

 

I want to mention something else. if you already have an "H-bridge" signal with no limits then just "steer" it to operate the 12 V relays in a fwd/rev direction and incorporate the limit switches.

This https://www.pololu.com/category/12/rc-servo-controllers link might help your second question.