Actually, I just received a coupon the other day for a precision scale, and that reminded me about this idea. Haven't picked up the scale yet, but likely will within a few days; I have to go to the far side of town to get it - and this is place is quite spread out.

Just recently built a programmer for some PIC16F877 and PIC16F887's I acquired, so will probably go that route. It's overkill for this project, but sometimes you use what you have.

 

Hey again SgtWookie

Thats quiet a lot of legs on those PIC chips and they are a bit expensive, expecially the first one, but okay, if you have built it why not use it;D

Is your system going through a computer or are you building a device in wich you can put your wished weight?

Ive going to the electric store tomorrow and get some tools, so I can open my scale op and have a look.

What scale is it you intend to use?

 

The PIC16F877/877A's are actually discontinued. The 887's are the newer generation. There are differences in the ICs; for one the parallel I/O was discontinued - but that won't affect this.

The 88x series are actually pretty inexpensive; I paid under $2 US for them.

I have some 2x24 HD44780-based LCD displays, and a few bubble-type touch keypads I might use for interfacing for input.

The nice things about these keypads is that they're sealed, the price was right, and I have them. The not-so-nice part about it is that I got them surplus, and you will be on your own to find something suitable. However, I'll endeavor to document the source code in a manner that it will make it reasonably easy to use a different keypad.

Drat, I just discovered that the scale I was considering is out of stock, and they won't be getting any more. Well, better to find that out, than design for an already obsolete product.

 

Yes that would be a waste of time.

At the beginning I thought of a device with a keypad and LCD myself, but it seemed to be more difficult for me to make, but if you would like to share your work with us all, that would be great. To have a complete unit insteed of using a computer would be the best way of doing this and would look similar to the once you can buy.

Have you made any thoughts about how the mechanics should work? Are you going to build it all up from scratch or are you using a powder trickler with the motor on as feeding device?

Ill see if I can post some pictures of my scales inder tomorrow.

 

I built a powder trickler several years ago from PVC pipe and fittings. I treated it so that it would be partially conductive, to eliminate any hazard from static electricity. I just used an electrical handy-box as a base, a piece of 1/4" stainless tubing with a hole in one side (inside the cylinder to admit the powder flow) and a small knob for a potentiometer to have something to turn. It's nothing fancy, but it does the job - manually, of course.

Due to possible safety and reliability issues, stainless steel and brass are probably the most suitable materials for consideration.

 

oh I see, that sounds somehow easy to build and you just connect the motor on that device to the automated circuit with the scale, LCD and the keypad and you have your own automaticly powder dispenser. I am looking forward to hear about your progress and looking forward to build my own one as soon as the automated part of the project gets solved.

I know that I cant be much of a help with this, because I do not have that much electrical/programming skills, but atm. I am reading about PIC programming, so maybe it can help me understand the project when it is finished and maybe someday I can develop some new features on my own and share them with you guys.

 

I have now opened my scale and I see the following (I havnt got my camera here atm.): The scale device itself is connected to the scales circuitboard by 4 wires. There is a capacitor on the back of the circuitboard. On the front of the circuitboard there is a LCD display, wich has 16 pins. There is a PIC marked: T24C02A 9b28s2. There are 4 switches, (tare, on, off and mode). There are some resistors I think, they are marked C1 to C11, but maybe it is capasitors too??

The PIC is a EEPROM (I dont know the difference atm), and as far as I can find out, it has the partnumber: AT24C02AN-10SC-ND.

Isnt it harder to make a keypad work, than just have some buttons for each digit on the LCD you want to alter? Lets say have one for the 1, one for the 10s, one for the 100s and one for the 0,1s?

A nice feature would be to have two potmeters so you could adjust the start-speed and the slow-down speed to compensate for bulky powders. Then you could fine tune the device to throw the charges as fast as possible.

I imagen this: Type in the wished weight you want, press Enter (or a similar key), then type in the slow-down speed weight (lets say 10 grains under the wished weight) and press enter and then press a start button to make it throw. It then remembers this ontill you press a reset button or take the power away from the device.

 

What about this site, can that be used to something?

http://docs-europe.origin.electrocomponents.com/webdocs/0099/0900766b80099349.pdf

 

I have now opened my scale and I see the following (I havnt got my camera here atm.): The scale device itself is connected to the scales circuitboard by 4 wires.

Probably a typical Wheatstone bridge configuration.

There is a capacitor on the back of the circuitboard. On the front of the circuitboard there is a LCD display, which has 16 pins.

Any part numbers on the LCD? How about part numbers on ICs located on the LCD display? 44780 is a very popular LCD controller.

There is a PIC marked: T24C02A 9b28s2. There are 4 switches, (tare, on, off and mode). There are some resistors I think, they are marked C1 to C11, but maybe it is capasitors too??

Reference designators beginning with "C" are almost always capacitors.
Reference designators beginning with "R" are almost always resistors.

The PIC is a EEPROM (I dont know the difference atm), and as far as I can find out, it has the partnumber: AT24C02AN-10SC-ND.

The "C" in the PIC part number denotes a one-time program device.
If the "C" were an "F", it would be a flash programmable device.

Isn't it harder to make a keypad work, than just have some buttons for each digit on the LCD you want to alter? Lets say have one for the 1, one for the 10s, one for the 100s and one for the 0,1s?

Were I to do something like that, I'd use </> buttons for digit select, and ^/v to increment/decrement the digit.

A nice feature would be to have two potmeters so you could adjust the start-speed and the slow-down speed to compensate for bulky powders. Then you could fine tune the device to throw the charges as fast as possible.

I'm thinking more of an automatic "learn" mode for a type of powder. If you start using a new type or new lot of powder, the trickler would need to go through an initial learning process to determine the optimal rate for dispensing that particular type and lot of powder.

Just for clarification, there are three very general types of smokeless powders that are commonly used:
1) Flake - very flat, fast-burning powders, usually used in very small amounts. The shape may be irregular or round. Some flake powders have a hole in the center, like Unique.
2) Cylindrical - moderate to slow burning powders. The powder may or may not have a hole through the center.
3) Ball - Moderate burn rate. I don't currently use ball powders. Accurate trickling of ball powders may be more problematic than the other types.

If you are using other types of powders that I am unfamiliar with, you should tell me about them.

What are your most commonly used powders?

I imagine this: Type in the wished weight you want, press Enter (or a similar key), then type in the slow-down speed weight (lets say 10 grains under the wished weight) and press enter and then press a start button to make it throw. It then remembers this ontill you press a reset button or take the power away from the device.

I'm thinking more on the capability of the trickler to save a variety of loads, and to be able to recall them even after power has been removed for long periods of time. This is one good reason to use a reasonably capable uC such as the PIC16F88x series; it has 256 EEPROM memory locations available.

Not all of those 256 locations will be available for saving loads, of course. Some could be used for the learned dispense rate for individual powder types, and various other bits of data that need to be retained.

 

oh I see, that sounds somehow easy to build and you just connect the motor on that device to the automated circuit with the scale, LCD and the keypad and you have your own automaticly powder dispenser. I am looking forward to hear about your progress and looking forward to build my own one as soon as the automated part of the project gets solved.

I'm thinking the automated version will need two separate stages of dispensing:
1) A worm-screw type arrangement for more rapid initial "bulk" dispensing.
2) The simple rotating tube for the fine metering.

I know that I cant be much of a help with this, because I do not have that much electrical/programming skills, but atm. I am reading about PIC programming, so maybe it can help me understand the project when it is finished and maybe someday I can develop some new features on my own and share them with you guys.

You might consider picking up something like a PICkit-3, or perhaps build your own ICSP or other type programmer.

 

What about this site, can that be used to something?

http://docs-europe.origin.electrocomponents.com/webdocs/0099/0900766b80099349.pdf

That would be useful if considering building a scale from scratch. I do not have the tooling or materials to attempt this.

 

The capasitor on the back is marked: T220nJ63

On the LCD display is there no partnumber. I thought there was on the back, so I bend it slightly up to look, but the LCD was transperant. I could see right through tho there was like a film/shadow on it, wich made it dark to look through.

I am not sure the "learned" automatic will work as well as a manual option to fine tune the speed of the motor, but I may be wrong.

I think the save option is a good feature, but for me it isnt nessesary, because I have all my reloading data on the computer, so the weight can be recalled whenever needed and fast.

I am not sure about the partnumber of the PIC, that was one I found on another site searching for the T24C02A.

I use various types of vithavuori, N165, N560, N550, N150.

For my shotshells I use Alliant Steel, but I think i go over to the vithavuori powders here too.

Do you think this project is getting big? I mean, will it be something a less skilled electronic man like me can build? The mechanics isnt a problem, but i am a little worried about the electronics and programming, but maybe it isnt too hard.

 

You might consider picking up something like a PICkit-3, or perhaps build your own ICSP or other type programmer.

Late last night I tried to find a simple PIC programmer, so I could build this before this project evolved and would need this type of device to do the programming of the PIC controller(s).

 

I was wondering, isnt there a simple way to build a device that contains an LCD display and a few switches (maybe the arrow-system you mentioned) and then connect it to the scales LCD display, have a PIC controller compare the numbers on the two displays and when they are the same, they shut down a motor. Then the only thing needed would be to program the PIC controller to slow the motor down when the right weight gets near. That would be a very simple system, that may work out as a nice automatic powder dispenser v1.0?

 

The capasitor on the back is marked: T220nJ63

220nF.

On the LCD display is there no partnumber. I thought there was on the back, so I bend it slightly up to look, but the LCD was transperant. I could see right through tho there was like a film/shadow on it, wich made it dark to look through.

I see. So, that means no backlight, correct?

I am not sure the "learned" automatic will work as well as a manual option to fine tune the speed of the motor, but I may be wrong.

The most important function will be the repeatability (accuracy) of the dispensing by weight. Attempting to perform this adjustment manually will be tedious and error-prone. Once the dispensed powder has gone over the weight limit, the charge will have to be re-cycled into the hopper, so the time and effort to dispense that charge will have been wasted.

I think the save option is a good feature, but for me it isnt nessesary, because I have all my reloading data on the computer, so the weight can be recalled whenever needed and fast.

You should keep a printed log of your loads. Additionally, each box of loads should have all load data affixed to it.

I am not sure about the partnumber of the PIC, that was one I found on another site searching for the T24C02A.

I see.

I use various types of vithavuori, N165, N560, N550, N150.

For my shotshells I use Alliant Steel, but I think i go over to the vithavuori powders here too.

I've never used Vithavuori (sp?). I mostly use IMR and Hodgdon powders, simply because I grew up with my Dad using them.

Do you think this project is getting big? I mean, will it be something a less skilled electronic man like me can build? The mechanics isnt a problem, but i am a little worried about the electronics and programming, but maybe it isnt too hard.

Connecting an external PIC to the LCD display (actually, the outputs of the existing scale PIC) is one item in question. I don't know what kind of soldering skills you may have, but if you goof that part up, you will be throwing that one in the trash and buying a new scale. At this point, you may have already damaged the one you have. I would not trust it until after verifying it against a manual scale, and a broad range of weights.

Once the LCD I/O pins have been determined, it should not be terribly difficult to intercept the LCD commands and convert them into usable information.

Building the actual device and circuit are other skills you will need to have. You will need to etch and drill a circuit board, and connect external components. You will also need to select suitable motors, and be able to mechanically interface them with the trickler.

Tell me, does your computer have a 9-pin RS232 port?

 

I was wondering, isnt there a simple way to build a device that contains an LCD display and a few switches (maybe the arrow-system you mentioned) and then connect it to the scales LCD display, have a PIC controller compare the numbers on the two displays and when they are the same, they shut down a motor. Then the only thing needed would be to program the PIC controller to slow the motor down when the right weight gets near. That would be a very simple system, that may work out as a nice automatic powder dispenser v1.0?

That won't work, as it would always overshoot the desired weight.

Trust me on this.

 

I have a adaptor from RS232 to USB and on my stationary computer I have such a port too, so I think I am covered on that point.

I know that it would overshoot, but that would bring the project one step closer to the finished product.

The LCD has backlight. The LCD is laying on top of a peace of plastic in wich there is a blue LED.

I wouldnt dear to think that I can calibrate the scale manuel, but by having the ability to change the start and slow-down speed would make it very easy to adapt the dispenser to new powders. First you try with full speed on the start-motor and set the slow-down-weight low. Then set the slow-down speed to low and see if the dispenser can handle it. If not, then slow both steps of dispensing down, untill the dispenser throws accurately enough every time.

If the dispenser has a specified start speed, a specified slow-down-weight and a specified slow-down speed, then I think it would be to locked. The user wouldnt be able to make adjustments to the dispenser, wich may help the dispenser throwing difficult powders.

I do have all my load data on paper too!

I am famliar to making PCBs and I have build a few power supplies and PWM circuits, so I am not totally new to it, but I havnt invented those circuits.

 

I have a adaptor from RS232 to USB and on my stationary computer I have such a port too, so I think I am covered on that point.

Ok.

I know that it would overshoot, but that would bring the project one step closer to the finished product.

So, how is building something that I already know won't work, help to get things done more quickly?

The LCD has backlight. The LCD is laying on top of a peace of plastic in wich there is a blue LED.

Hmm. And the blue LED is powered by a couple of the traces in the 16-line connector, correct?

I wouldn't dare to think that I can calibrate the scale manually, but by having the ability to change the start and slow-down speed would make it very easy to adapt the dispenser to new powders. First you try with full speed on the start-motor and set the slow-down-weight low. Then set the slow-down speed to low and see if the dispenser can handle it. If not, then slow both steps of dispensing down, untill the dispenser throws accurately enough every time.

It's going to need more than two "steps", or two speeds. You can't stop a motor instantly for a variety of reasons, including basic physics.

the dispenser has a specified start speed, a specified slow-down-weight and a specified slow-down speed, then I think it would be to locked. The user wouldnt be able to make adjustments to the dispenser, wich may help the dispenser throwing difficult powders.

There is no reason why the dispenser can't figure this out all by itself - and be better at it than one could do by hand.

I do have all my load data on paper too!

Good!

I am famliar to making PCBs and I have build a few power supplies and PWM circuits, so I am not totally new to it, but I havnt invented those circuits.

OK.

 

No the backlight is not powered by one of the 16 pins. It is powered by the circuit board.

Well if it can be done to do it more precisely then it diffinently would be the way to go. I just didnt think it could be programmed to do this.

I am looking forward to hear your process when you get the scale and see for yourself how it can be done.

You said you would use a keypad and a brushless motor, I have found these listed below, do you think they could do the job?

http://www.dealextreme.com/details.dx/sku.12829

http://www.dealextreme.com/details.dx/sku.4935

I may be asking to many quiestions and write some stupid lines, but I am not that good at english and sometimes I may be hard to understand and maybe I dont always understand what you are writing, but I hope you bear over with me.

 

No the backlight is not powered by one of the 16 pins. It is powered by the circuit board.

OK. Anyway, it is pretty common for LCDs to have 14- and 16-pin interfaces. As I already mentioned, one of the technical problems is determining what the signals to the LCD are. If you don't have at least an O-scope, or preferably a logic analyzer, that portion will be (to say the least) difficult. You may need to build some test equipment to determine what's really going on with your particular hardware.

Well if it can be done to do it more precisely then it defiantly would be the way to go. I just didnt think it could be programmed to do this.

Cartridge loads have terminal ballistics. Motors have ballistics, too - it's on a much smaller scale and lower power levels, of course.

I am looking forward to hear your process when you get the scale and see for yourself how it can be done.

You will need to have some patience on this. Enthusiasm is good, but it must be tempered with some experience. Your ideas aren't all that far off, but this will require a good bit of thinking through. Any errors must be immediately reported, so that an overcharge situation can be avoided; as such situations could result in damage to property or the operator.

While I'm on this train of thought, the problem of overcharges weighs (sic) heavily on my mind.

A better solution would be to:
1) Weigh the cartridge itself as empty. If the cartridge weight is significantly over/under the previous cartridge weight, report it.
2) Dispense the desired charge weight into the cartridge.
3) Inform the operator if the charge is within tolerance or not, indicating if the projectile is ready for seating.

You said you would use a keypad and a brushless motor, I have found these listed below, do you think they could do the job?

(links omitted)
Those are "mystery motors". They're available now, but their specifications are unknown, and they may not be available in the future. It would not be good to design something that could be used by a number of people around a motor that may be shortly unobtainable.

I have a number of PF35T-48L4 stepper motors that were designed to operate from 7V. These are widely available in the States (Jameco.com stocks them) and are very inexpensive. They are brushless, because they are stepper motors. They will operate just fine from 5V, as will a PIC uC. This will simplify design considerations. Using stepper motors will enable very precise control over the dispensing of powder; I feel that it will be far more suitable than a BLDC motor.

I may be asking to many questions and write some stupid lines, but I am not that good at English and sometimes I may be hard to understand and maybe I don't always understand what you are writing, but I hope you bear with me.

We are separated by oceans and language. But we share a common bond (a love); an enthusiasm (excitement) for taking a firearm (rifle, pistol, shotgun) to a range and performing well with it.

You are not asking too many questions.
You are not writing stupid lines (making stupid statements).
This is an exchange of ideas, and it is expected that many questions need to be asked, and answered. Some questions may take a while to resolve (be answered in a helpful way).

English is a language that is very hard to learn. I will say that you are writing very well in the English language. If I were to try to communicate in your native language, you would probably think that I was an idiot (stupid, a moron, or otherwise mentally impaired).

If you have a hard time understanding something that I have written, please ask me to explain it (make it more simple).

It is very important that you understand everything, and at the same time, if I ask for more explanation of something you have said, I hope that you will provide it.