Help using a operational amplifer as a 2 position latch circuit

Thread Starter

sornjs

Joined Dec 29, 2017
29
Attached is a modified #37 to determine where to put the SW1 reset capacitor. I would bet on to the left of the resistor allltlhough I did'nt do so good in 22, 23 above.
Since one motor stalls @16 ma. 50 of these and should draw about .8 amps?
Place I use for parts (salvage electronics) and the one dual voltage power supply they they have is 1.5 Amp on tht +12, .5 Amp on the -12. NOT GOODCONTROL DIAGRAM0001.png
Can i use 2 - 12v units connected together in series as a dual voltage unit?
The perxon I talked to said he is going to check if he has any power supplies I can connect in series.
 

AnalogKid

Joined Aug 1, 2013
8,227
Any particular reason for not going with #29 and a single +12 V supply? It isn't as complicated as it might look (no additional connections or parts), and unless one end of each motor *must* be common-grounded, I would think the simplicity (and lower cost) of a single output supply would be a better system-wide choice.

ak
 

Thread Starter

sornjs

Joined Dec 29, 2017
29
Jacksonville, Fla. I agree a single voltage supply circuit is better. One conrtol per ic keeps is simple and should not affect const much.
A dual voltage system requiers allociating power for all, or at least some, of the turnout control circutis to both power supplies.
This seams unproductive. I plan on using such power supplies for lights, signals, etc and could not know what was available from a dual voltage slystem.
I will buy one 12v supply now and others as (if) i need them.
 

xox

Joined Sep 8, 2017
382
Not to mention cheap op amps abound. You can find LM324's online for less than a quarter apiece, for example...
 

Thread Starter

sornjs

Joined Dec 29, 2017
29
Looks like ckt #29 and LM324's

Does it hurt to install both reset capacatiors and cut out the one i don't need?
I could build a few all alike and then remove the wrong reset cap?

I was asked what watage resistors i needed. I guessed 1/4 or 1/2 watt.
???
 

Thread Starter

sornjs

Joined Dec 29, 2017
29
Circuit #29, on the upper right of the drawing, showes a capacatior between gnd and +12v..
Does that mean I install one at the soruce?
 

AnalogKid

Joined Aug 1, 2013
8,227
Circuit #29, on the upper right of the drawing, showes a capacatior between gnd and +12v..
Does that mean I install one at the soruce?
That is a decoupling capacitor, a universal requirement for analog circuits. The general rule is one cap to ground per IC power pin, located as close as possible to the IC and with short leads. In you case one of the power pins already is connected directly to GND, so one cap per part.

Full disclosure - since the opamps in your circuit are not acting as linear amplifiers, but more like a saturated switch, the cap will not improve circuit function (such as stabilizing the forward gain equations or preventing positive feedback and oscillation). It will act as a two-way noise filter, both reducing noise that the circuit can put on the power wires, and making the circuit less susceptible to noise spikes coming in on the power wires.

1/10th watt resistors or higher.

ak
 

Thread Starter

sornjs

Joined Dec 29, 2017
29
searching for parts.
I decided to use a quad op amp to save cost of pcb and socket.
Is LM324M the correct one?
What should i search for to get the printed circuit board?
 

xox

Joined Sep 8, 2017
382
searching for parts.
I decided to use a quad op amp to save cost of pcb and socket.
Is LM324M the correct one?
What should i search for to get the printed circuit board?
The LM324 will work fine. It's a somewhat mediocre amplifier but you're just using it as a switch anyway, so nothing to worry about there. And you can order cheap PCB's from a site like jlcpcb.
 

Thread Starter

sornjs

Joined Dec 29, 2017
29
XOX
I can't figure how to use theit layout program.
Here's a copy of what I came up with as a "pcb" layout.
Can you give me any assistance.DETAILED CKT.png
 

Thread Starter

sornjs

Joined Dec 29, 2017
29
Thanks again all. Could not figure out desing program to create exact board.
Fourn an existing board i can use easily.

THANKS ALL.
 

sghioto

Joined Dec 31, 2017
1,038
Here's another version using a CD4069 inverter.
According to the "Tortoise" documentation it takes three seconds to complete the throw. This design will operate the motor in either direction for about 9 seconds. At power up both outputs will remain low and after each operation for zero current standby even though the documentation says the motors are designed for continuous "stall" at 16 ma.
Steve G

EEE CD4069 motor driver.jpg
 

AnalogKid

Joined Aug 1, 2013
8,227
Here's another version using a CD4069 inverter.
Yeah, I mentioned this approach (using 555'5) in post #28 but no one picked up on it.

I recommend a CD40106 hex inverter with Schmitt Trigger inputs for more crisp transitions (and lower power dissipation) between the high and low states. It is important to remember that a CMOS inverter is basically a high gain linear amplifier with a gain of something like -10,000. With the very slow ramp on the inputs, there almost certainly will be a noise burst on the outputs as the ramp voltage wanders across the input stage transition region.

Separate from that, there is no way the three gates in each group all are going to change state at the same time. This means that for a part of each activation cycle, the gates will try to put a dead short across the power source for a few, and possibly hundreds of milliseconds. This will lead to premature component failure. Schmitt Trigger inputs will reduce, but not eliminate, the timing difference among the gates because the Schmitt transition levels are more tightly controlled than the normal transition levels. I've used this design technique many times without problems, but many large companies have in-house design rules that prohibit the direct paralleling of totem pole output stages.

ak
 
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