Solenoid driver

[earckens]

Drawback again is that you have to reset the switch back to "neutral", or center position each time after having pressed the pushbutton.

Sorry for the nitpicking

 

[chemelec]

Drawback again is that you have to reset the switch back to "neutral", or center position each time after having pressed the pushbutton.

Sorry for the nitpicking

THERE IS NO PUSH BUTTON!
THIS DPDT SWITCH IS ALSO REPLACING That PUSH BUTTON!

 

[alec_t]

How about this? It needs one such circuit per turnout, but does enable an ON-ON SPDT toggle switch to be used both to trigger a pulse (about 0.6 sec with the components shown) and to provide the required direction indication.

 

[earckens]

THERE IS NO PUSH BUTTON!
THIS DPDT SWITCH IS ALSO REPLACING That PUSH BUTTON!

Sorry chemelec, I assumed you still used the circuit in upload here.

Now how should it look like?

 

[earckens]

How about this? It needs one such circuit per turnout, but does enable an ON-ON SPDT toggle switch to be used both to trigger a pulse (about 0.6 sec with the components shown) and to provide the required direction indication.
View attachment 101582

Impressive! Where do you get that program from, what is that?

However, one circuit per turnout? Not economical I think, and centralisation is important to facilitate later extensions, expansions, automation projects,..

 

[KeepItSimpleStupid]

One circut would not be too bad once in PCB form. If you need 50 TAs to be conrolled multiplexng can be used or a large I2c bus where each driver can control 16 things. More difficult than it sounds. Nonetheless you can stil multiplex with a high and low side driver. You can multiplex the inputs too. You could store the state in FRAM. The micro does the pulsing too. With two 16 chnanel I2C output chips you can have 250 ish solenoids with 32 driver chips and if you want you can control with I2C and a couple of chips. 16 bits can be reduced to 4 with a priority encoder. So about 8 bits for about 250ish solenoids.

 

[chemelec]

Impressive! Where do you get that program from, what is that?

However, one circuit per turnout? Not economical I think, and centralisation is important to facilitate later extensions, expansions, automation projects,..

Still Requires the Center Off Switches and it will Work but Costs more since you need one of these circuits for each set of Solenoids.
Also the Heat in the Mosfet will Increase as the Gate Voltage Decreases.

 

[chemelec]

Sorry chemelec, I assumed you still used the circuit in upload here.

Now how should it look like?

See POST 70, But Where it Says Trigger, That is just the Terminals on the PCB.
They Now Connect to the DPDT Switch, which Replaces the Push Button.

 

[alec_t]

Where do you get that program from, what is that?

It's LTspice, a free download from Linear Technology.

 

[alec_t]

Still Requires the Center Off Switches

No, it doesn't. Current pulse lasts only while C1 or C2 is charging.

the Heat in the Mosfet will Increase as the Gate Voltage Decreases.

MOSFET dissipation is ~8W for ~60mS, once per actuation of the solenoid. So average power is negligible. No heatsink necessary.

 

[earckens]

See POST 70, But Where it Says Trigger, That is just the Terminals on the PCB.
They Now Connect to the DPDT Switch, which Replaces the Push Button.

Great!! One switch per turnout, no pushbutton,

If your Supply is 15 Volts, Than the Zener and the 680 Resistor are Not Required.
I'm Sure One of your drawings showed 25 Volts to the Solenoids.

Sorry for the confusion chemelec! Thanks for your help.

 

[earckens]

See POST 70, But Where it Says Trigger, That is just the Terminals on the PCB.
They Now Connect to the DPDT Switch, which Replaces the Push Button.

Great! Would the SPDT switch (ON)-centerOFF-(ON) switch not have to be one where the center position is the standard rest position?

 

[earckens]

alec_t, your proposal requires one pcb with components per turnout: this is not only more expensive, it would also require 3 wires from the control panel to each turnout, same as with a centralised solution (chemelec).

 

[earckens]

Case 1: SPDT ON-ON switches cost €2.23/10, plus the DPDT pushbuttons @ €3.84/10 versus Case 2: DPDT (ON)-centerOFF-(ON) switches that cost €6.80/10. Case 1 also requires more wiring, so cost still higher. Chemelec, your last proposal is the best.
Except in case 2 I have to provide LED feedback on turnout position because a center-off switch does not show that.
In any case, thank you all for your thinking, Erik

 

[KeepItSimpleStupid]

Something I tried to post from my cell earlier in the week didn;t post for whatever reason.

The general idea is to matrix the switches, so a 16 x 16 matrix could control 200+ solenoids (exact number not 255 because of 0,0 is an off condition.
You could design the board to accommodate 16 high side drivers and 16 low side drivers. To save $, don't populate. If you need 16, use a 4 x 4 matrix. If you need more start populating drivers. e.g. 4 x 5 or 5 x 5.

The number of bits can be reduced from 32 to 8 if you use a 4 line to 16 line decoder (not sure if they are made), but I think they are.

One bad thing is that the high current lines are run.

An I2C BUS to I/O port may be able to control them.

Keep the state of the switch in FRAM which can be I2C based. No batteries are required and should have an unlimited lifetime.

Another problem is how to say use the state to activate a crossing light. Well, if you need it, hopefully you can use a limit switch.

 

[KeepItSimpleStupid]

In terms of activation, you can multiplex that too, and save on ports. Look up a typical keypad. Analog Devices has an IC that will decode a huge keypad to off load processor work.

 

[earckens]

KeepItSimpleStupid, as I understand it your idea of a matrix is good, except I do not see how you replace DPDT-center-off switches in there.

 

[chemelec]

earchens, I think my design is about the simplest overall, but I leave the final decision to you.

If you needed a PCB, I could do one up for you and mail it to you.
No Charge!

 

[earckens]

Chemelec, I agree with you: your design is just the best and will be used on my layout; all here have contributed so much, and in the end a lot come out of here. This board has given me so much in terms of information, friendship, help, sociability and feedback.. I feel in debt to you all.
Your offer of a pcb I gladly accept, I appreciate it a lot but I would like to know how I can return the favour: pm me anytime, I gladly reply.
Have a good day,
Erik

 

[KeepItSimpleStupid]

If you really wanted too, you COULD use a keyboard such as this one: https://store.digilentinc.com/pmodkypd-16-button-keypad/

e.g. 001A is one way, 001B is the other.

Here https://store.digilentinc.com/pmodioxp-i-o-expansion-module/ is actually an 11x8 encoder. You can keep your switches if you want to, but you can decode up to 88 keys with this decoder.

it's just some ideas.