Hello all, new to the site. I have a little electrical knowledge, probably enough to get me in trouble, ha. So, some of the electric terminology that I use in this description probably isn't understood by some on this site. So, I will provide as much information as I can. Sorry for the long post, just trying to give as much info as I can.

I'm currently working on a project with my son and have a few questions. I have attached a drawing of what I'm trying to accomplish. His project involves a beam scale that when weight is added will allow the beam to move in the upward direction.


Here is the scale being used for the project. It's basically a lab balance beam scale.


As weight is applied, the beam will move upward toward the target point of 0.
There is a brass beam plate that extends out the back of the scale. It's a flat brass plate. In this pic, you can get an idea.



I have 2 IR optical Sensors from a 12v source. The picture attached in the details below show how it is setup.

Placement of these sensors is critical because accuracy is the upmost importance, thus the adjustment screw that is 3D printed.

The beam will go back down to the resting point when the weighted pan is removed. The object of the project is the fill the pan as fast and precise as possible to reach 200g of weight and do this 10 times. Fastest time wins.

The 12v motors will be coupled to a 1/4" brass tube about 4" long that will dispense very small lead BB's. These BB's will exit the brass tube and fall into the pan. Thus, the using of 2 separate rpm motors. The motors will not be cranking up the beam, just dispersing the BB's like an auger. So when the relays energize the state in which I want, the motors will stop immediately. Once the pan is removed, dumped and replaced back on the scale, the motor are off awaiting on the start button yet again to be pressed for the next cycle.


The Project:

• main power switch to power on everything from a 12v source.
• start switch - will be the main switch to operate the system. It will power both Mini Econ motors to drive the beam upward.
• Mom on Switch - will only be used if fine tuning is needed and will be a (Mom - on) switch that bypasses the IR sensors to get the beam at the precise location.

Sequence

1. Turn on main power switch.
2. Start switch will power both motors to turn simultaneously.
3. While both motors are running, the beam sits idle in the bottom IR sensor. Which will allow the faster motor to run.
4. When the beam starts to move upward and clears the bottom sensor, the faster motor (227-rpm) will shut off.
5. Now the beam is between the bottom IR sensor and the top IR sensor while only running on the single slower 65-rpm motor. This slower turning motor allows the beam to rise at a much slower pace for a precise stop.
6. The beam continues to rise on only the 65-rpm motor, until it reaches the top sensor.
   Once the top sensor is breached, power is killed to the 65-rpm motor.
7. The top Sensor can be fine-tuned for precise stops. But if stops are not precise, the Momentary push button switch will allow “bumping” of the slower motor to get the beam to the precise location. It must override the IR sensors to get to the precise stopping point.
8. Now the beam has reached its accuracy point of "0", both motors are off.

The system works flawless and works as it should, except for 1 hiccup. The one thing that I didn't think off came back to bite me in the testing. Once the pan is full of 200g of lead BB's, the circuit and the system is idle. Nothing is happening.

(this is the mess up) You have to remember to turn off the start switch before the next cycle. When I removed the pan of lead BBs to dump back into the hopper, the beam scale returned back to its resting point and the circuit started again dumping BB's all over the table.

Now that everyone is somewhat confused, here is my question.

Is it possible to replace the "start" switch, which is a simple SPST on/off switch with a Momentary push button switch? I could use a latching relay on the Mom start switch that would latch in and allow a single press of the button to energize the circuit and allow the cycle to run. But..... I need it to return to an unlatched state when the pan is removed. So every cycle must be started with a press of the mom start button.

I even thought of a timed latch relay, however in this project, speed & accuracy is the key. Too much time and your waiting. Too less time and the circuit starts again dumping BBs all over the table.

So, if you guys have any suggestions, I'm all ears. But I would like to set it up so that every press of the button will start a cycle, then once the cycle is complete, it will return to a "ready state" for the push of the next cycle.


Thanks
Titans7

 

The below Schematic is an automatic Gun-Powder-Dispenser that I designed a while back,
maybe it will be useful to You, or give You some ideas to work with.
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To be honest, the project is using a DIY powder dispenser for reloading. Just dispensing lead BB's instead. And the scale is also a reloading scale. They are trying to make the school kids think outside the box. I'll have to look up the symbols and such, not familiar with electrical symbols, but I'll give it a shot.

 

Once the pan is full of 200g of lead BB's, the circuit and the system is idle. Nothing is happening.

Can you install a sensor at the "0" stop point on the scale?

 

All of the Symbols have a brief description and a part-number in the Schematic.

All part-numbers are DigiKey-Electronics part-numbers.

The Optical-Switch may actually be the exact same part as You are currently using.

Go to DigiKey-Electronics-website and enter in the part-numbers for
current pricing and availability, as well as the Specification-Sheet-PDF file.

If You have further questions, just ask,
there are many old-farts here that can just glance at the Schematic and tell You all about it.

The basic operation sequence is this ..........

The Balance-Beam "Flag" is initially not blocking the Light from the LED going to the Photo-Transistor,
because there is no weight trying to move it down.
Press the Start-Button to start the dispensing Motor.

After the Scale-"Flag" has moved down because of the added weight, and has blocked the light from the LED,
the dispensing Motor will stop, and remain stopped, until the Push-to-Start-Button is pressed once again.

If the Button is pressed momentarily, under any condition,
the Motor will always run, this is called "Jog"Mode,
this is for adding slightly more BB's than the Scale is adjusted for.

The Pot is for adjusting the Motor speed, it should be a 20-turn Trim-Pot.

Do You know how basic Electronic-Components work ?
Which ones are creating confusion for You ?
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Can you install a sensor at the "0" stop point on the scale?

There is one. The top sensor is adjustable up and down, so that when the beam approaches 0, it will trip the top optical sensor and shut everything down. The only problem is "IF" you forget to turn off the start switch, once the pan is removed to dump, the cycle repeats itself. Like I mentioned to LowQCab, I don't really understand the symbols. I did however look up all of the items on his drawings and still have no clue.

 

I understand the problem
One solution is to have a relay that is started with a momentary switch and latched using power for the slower motor.
When that motor shuts OFF the relay deactivates.
But then that other momentary "bump" switch would need to be wire to the power switch side.
Does this make sense?

 

All of the Symbols have a brief description and a part-number in the Schematic.

All part-numbers are DigiKey-Electronics part-numbers.

The Optical-Switch may actually be the exact same part as You are currently using.

Go to DigiKey-Electronics-website and enter in the part-numbers for
current pricing and availability, as well as the Specification-Sheet-PDF file.

If You have further questions, just ask,
there are many old-farts here that can just glance at the Schematic and tell You all about it.

The basic operation sequence is this ..........

The Balance-Beam "Flag" is initially not blocking the Light from the LED going to the Photo-Transistor,
because there is no weight trying to move it down.
Press the Start-Button to start the dispensing Motor.

After the Scale-"Flag" has moved down because of the added weight, and has blocked the light from the LED,
the dispensing Motor will stop, and remain stopped, until the Push-to-Start-Button is pressed once again.

If the Button is pressed momentarily, under any condition,
the Motor will always run, this is called "Jog"Mode,
this is for adding slightly more BB's than the Scale is adjusted for.

The Pot is for adjusting the Motor speed, it should be a 20-turn Trim-Pot.

Do You know how basic Electronic-Components work ?
Which ones are creating confusion for You ?
.
.
.

Yes I know basic electrical concepts. Wired my house, shop, etc.

I think the 2 sensors I have controlling 2 separate motors is throwing me off. Like I mentioned, it works flawless and really well, "IF" I flip start switch to on, let it finish cycle, flip start switch to off, remove pan, dump, repeat. Its really just one more step to turn the switch off. I was just looking for a was to hit the mom start button 1 time, run the full cycle and then the "switch state" or power delivered to the relays would be off. Thus the cycle wouldn't repeat it self. Its really no big deal, was just looking for the "dumb non circuit trained" way. Ha.

 

I understand the problem
One solution is to have a relay that is started with a momentary switch and latched using power for the slower motor.
When that motor shuts OFF the relay deactivates.
But then that other momentary "bump" switch would need to be wire to the power switch side.
Does this make sense?

yes. I'm actually looking at my drawing now. I have another 12v dual relay module. I'm looking at a way to use the trigger from both motors to do as you mention.

Because, bottom sensor NC controls the fast motor and the top sensor NO controls the slow motor. Once the bottom sensor is cleared, thus now its NO, I could trigger a relay to kill power. However the top sensor is still active. So once the beam reaches 0, now both motors are shut down. I would need to figure out a way to have both triggers from both sensors "de-latch" a start power relay.

 

D

I would need to figure out a way to have both triggers from both sensors "de-latch" a start power relay.

Don't think so. I thought the slower motor runs continuously until the top sensor is activated, correct?

 

No, both run. It's a dual dispenser. Because the weight is so great, 1 slow motor will take too long. 1 fast motor will overshoot. Thus with a fast and a slow, both run to clear bottom sensor then the slower motor continues to run until top sensor. Gives more control. Here is simplified version of what I'm looking to do. Main power switch sends 12v to the Momentary start switch. Now remember, I don't have soldering tools and circuity items to do what was explained above, thus I looking into these complete units to control the system. And it works great except for the 1 flaw. So, what I need to do is see what can be added between the mom switch and the relay DC+ input so that it will latch power until the beam reaches 0. Once the beam is at 0 and the pan still on the scale, the input DC+ will be off.

 

Yes I know both run but the faster motor shuts OFF first while the slower motor continues to run until it hits the top sensor.
When the slower motor shuts OFF is what I want to use as a reset for the start relay.
What do you have on hand for relays or relay modules?

 

I have another 12v dual relay module like the one pictured. But I can get whatever.

 

Is the bump switch only used after the top sensor shuts OFF the slower motor?

 

yes. I have it to bypass everything and send power straight to slower motor.

 

ah, I see where your going. I'll need to jump power to the bump/jog switch from the main power switch. To illiminate it from the mom switch.

 

I agree with sghioto that you only need to to see the slow motor relay deactivate to unlatch the new start / stop relay.
This is my undersatnding of the sequence of events.
1 Start button pressed. this latches all three relays on.
2 Lower sensor becomes unblocked. This deactivates the relay for the high speed motor.
3 The upper sensor becomes blocked. this deactivates the relay for the low speed motor. We now need this to de latch the start stop relay. (NOTE the slow speed relay has been activated on since the start button was pressed.) You will probably need to add some diodes to to isolate the triggering signal from the start button from the latched connection on the start stop relay.
One thing I don't understand is that you seem to be feeding +12 volts from the battery to the 5 volt OUTPUT of the DC to DC converter.
Les.

 

oh crap that pic is backwards. Its fed 12v and drops to 5v.

 

Will need to order a different bump switch as it requires a SPDT set of contacts like this one.
Schematic for the new components:

 

Ok, no problem. Will this be for both the bump and the Mom start?