timer circuit needed

[john1]

Hi n5oxp,

Thank you for your description of events.

There are a couple of points i would just like to clarify.

I think i follow what happens, but you did not mention how the string
tying motor gets back to the start position. I would guess that when
the bale is discharged, the motor is moved back to its start position.

Unless its some kind of arrangement where the motor just moves a feed
of string like a pulley or a pipe, which flicks back after each
operation, ready for the next operation.

It seems odd that the motor moves.

*********

Ive just read your second post, you mention that the motor drives a
screw-feed which positions the string to be wrapped around the bale.

But the same question remains, it has to get back to the start point.

I think i will assume this is not a problem, as it has not been
mentioned, maybe it just flicks back after each wrapping.

You say that the sequence of events would always be the same, that is
start hay wrap and move across bale for one second,
stop moving across bale and allow string to wrap for eight seconds,
move across the bale for one second to get to second position,
stop and allow string to wrap for eight seconds,
move across bale for one second to get to third position,
stop and allow string to wrap for eight seconds,
move across bale for one second to get to fourth position,
stop and allow string to wrap for eight seconds,
move across to the edge into the cutter

This is where i lose the thread.
you say that at present it is done manually, and you want to allow
for adjustments to get the motor to stop at the right places.
Surely this assembly was made as an automated action?
Did it break down?
These adjustments, would you want to do these each time, or just get
them right and leave it?

I assume this arrangement would be done so that you could use it
un-attended?

So you would need some sort of indication if things foul up, unless
you can actually see the mechanism from your normal position.

Have you considered a cam assembly and a set of micro switches?
I still feel that this was probably originally intended to be
automatic, maybe you should check around the assembly thats already
there, you might find mounting positions for micro switches.

Have you any thoughts on this ?

John

 

[n5oxp]

Thanks for the responce John,
I didn't mention the initial movement at the start of the tying process because I had already planned to use a one shot to get it there. It will be on a seperate relay since the polarity reverses to change direction of the motor. It actually goes all the way across and then works its way back to home position. The trip back to home position is where all the tying takes place. It is not actually tying but just called that on a round baler. The string simply wraps around the roll of hay as it spins. The 16 sec pauses allow for 4 wraps of string and the 8 sec pauses allow for 2 wraps. This process can all be viewed from the tractor seat. It is correct that the process is intended to be done manually as this is a new hay roller. I have an indicator that I can view from the tractor seat that lets me know where to stop the string and let it wrap. I currently have a small box (came with the roller) that contains a simple SPDT switch that I flip on and off to the move the motor. The string flows through metal tubes that are attached to the screw drive motor in such a way as to pass in front of the roll as it is spinning. More expensive hay rollers come with "monitors" that mount on the tractor and automate the process as I am wanting to do. Some even have digital displays to guide the operator in the formation of the roll as it is feeding into the roller, making sure hay is evenly distributed across the roll.

 

[Sebi]

Just an idea...

 

[john1]

Hi Sebi,

Your diagram is neat and the use of a decade counter is
very tidy.

If an electronic answer is the way to go, that looks
very good.

Personally, i prefer micro switches, out in a field if
your stuck, you can poke them with your finger to see
that they work.
Electronics is not everyones cup of tea.
Many people are ok with wiring and switches, its when
things go wrong that causes most trouble.

John

 

[n5oxp]

Here is a crude drawing of the round roller mechanics for the string.

 

[nettron1000]

If im understanding it correctly your timing diagram should be something like this:

**broken link removed**


You could remove 16 seconds from the initial start-up of the timing cycle if you had a sensor such as a microswitch to let the circuit know when the "bale" is ready. This would simplify circuit layout.

 

[n5oxp]

You have the timing cycle correct except take the 16 from the end and put in at the beginning. Please tell me more about the microswitch

 

[nettron1000]

You have the timing cycle correct except take the 16 from the end and put in at the beginning. Please tell me more about the microswitch

Actually it doesnt matter if the 16 second delay is at the beginning or end in the timing diagram, it means the same thing. Its a loop remember.

About the microswitch; is there a place on the machine where you can mount it where a moving part of the baler can trip it and start the timing cycle ?

 

[n5oxp]

There is an indicator on the baler which moves downward as the roll size increases. I had planned to mount a switch on this indicator that would be physically adjusted to make contact once the roll was at the proper size. The timing cycle must start and stop and cannot run continuously. As I drive the tractor over the hay the roller picks it up and adds it to the roll inside. Once it gets to the proper size I stop the tractor and begin the string wrapping process. This matches the timing cycle. Once the string is on and cut, the roll is dumped and I begin to drive over the hay again and form another roll. The string motor is not moving while hay is going into the roller. Here is a link for pictures of the machine .**broken link removed**

 

[mechie]

Baler timer

Could this be developed to do the job?
The 555 is arranged as a monostable, a fixed 1/4 second pulse.
Each output pulse will increment the 4017 decade counter.
As each output of the 4017 goes high it will select a diferent charging
resistor for a capacitor which will charge up to the threshold of the
comparator (741 op-amp), this will cause the 555 to be re-triggered,
producing another pulse to increment the 4017 and simultaneouslt discharge the 4017's timing cap.
Every other output of the 4017 is dioded together to produce the motor drive sequence.
Every step of the sequence can be adjusted to generate any reasonable timing value.

As drawn there is no 'rest state', the circuit will (should?) sequence
forever but this is easily corrected by skippling a diode.

 

[n5oxp]

Thanks for the reply. I am not real familiar with the operation of the 4017. Will it automatically select the next output each time it is triggered? What about the off intervals in the timing cycle? Is there some way to generate the pauses between outputs?

 

[n5oxp]

I went back and reread your description and I think you a generating the pauses or off times by only connecting every other output and allowing those in between to only be used to retrigger the 555.

 

[mechie]

Loose strings

The 4017 is a dead common decade counter - each pulse on the input (clock) will
increment the counter, energising the next output (only that one output).
When the 4017 is reset (a simple addition to the circuit I drew) it goes back to outputting only
on the '0' output.

I intend that every output of the 4017 will retrigger the 555 (after a delay)
so that you will have ten seperate delays, each independantly adjustable.
The first delay is your 16 second 'dwell', so there is no output and the relay is not energised.
The second delay determines your 1 second long output pulse- relay energised.
The third delay determines your 8 second dwell- relay off.
Etc. etc.

As each stage is a seperate delay you can 'twiddle' with various timings to alter the string winding-
a panel of ten potentiometers could be placed in the tractor cab for on-field control.

Remember I said this is a 'concept drawing', it will require some development to finalise the arrangement :!:
But I see nothing that looks difficult here; the idea could be expanded to give more steps or less, as you get better at macrame :wink:
If a second 4017 were added (simple cascade for upto 19 outputs) then the 'return to start' could be a part of the circuit - reversing the motor shouldn't be difficult.

 

[nettron1000]

Ive yet again revised my original block diagram to include the longer intervals.
**broken link removed**

I thought my original idea had too many pots, the problem was in getting the longer intervals to "fit" in the timing range ( taps) of the 74154 multiplexor. This newer diagram uses one-shots to get those longer timing intervals.

The 555 timer as independent control of pulse length (high time) and pulse period (low time) via two potentiometers, R1 and R2.

The timer must be set so that the pulse length, high time, is 1 second and the pulse period, low time, is about 2 seconds, this will put most of the timing cycle within the range of the 74154. The One-shots take care of the longer timing intervals when they are triggered by the 74154.

POR is power- on- reset, I didnt include the circuitry for this because of size and clerity but its rather simple to add.

I didnt include the extra 16 second start-up delay, im assuming you are going to use the microswitch , which is tripped "on" by the baler indicator, to initiate the timing cycle.

Ive tested most of this circuit but not all.

Its not an ideal circuit since it still has quite a few pots to adjust but its the best i could come up with for now, im still tinkering with it.

I dont have any 4017's but i think that would be a better idea because it would elliminate the need for the counter IC and simplify the circuit alittle.

 

[n5oxp]

Thanks for all the input nettron. I think this idea is really starting to take shape. I may start rounding up some parts and see how the circuit works out with some leds. It would really be nice to just stop the tractor and watch the circuit do all the work. Not to mention when the timing was fine tuned the string would be wrapped on the bales with consistent spacing every time.