Multi Mode Timer

[Airman1]

Hi all,

I have just purchased a K141 Timer Kit.

I wish to do some adjustments to allow the timer to be triggered by a 5 volt pluse

Here is a link to the circuit diagram and operation
https://www.electro-tech-online.com/custompdfs/2011/05/multimodetimer.pdf

Do I just need to change the value of the resistor ?

Any info or help would be greatly appreciated

 

[Brevor]

Do I just need to change the value of the resistor ?

It looks to me like that would work.

 

[Airman1]

What value would do the job?

How do I work it out?

 

[Reloadron]

What value would do the job?

How do I work it out?

From the data sheet:

From the 4N25’s data sheet, the input
current required is 10 times the
output current. This means that we
need a minimum input current of 5mA
to trigger the timer.
The voltage across the optocoupler’s
internal LED, Vf, is typically 1V and
remains fairly constant regardless of
input current. Therefore, the minimum
input voltage necessary to trigger
the timer is given by:
Vin = (Iin x R1) + Vf
= (5mA x 1k
) + 1V = 6V
If lower trigger voltages are required,
then it’s necessary to reduce the value
of R1.

So for the opto coupler Vf = 1 volt and If = 5 ma.

If you want to use 5 volts:

5 volts - 1 volt = 4 volts / .005 amp = 800 Ohms.

Ron

 

[KeepItSimpleStupid]

R <= (5-1.2)/(10e-3) which is about 380 ohms. It requires a 1/2 watt resistor. 380 ohms is not a standard value so pick the next lowest value. There are different sets of values for 1%, 5% etc. resistors.

There is lots of slop here. I designed for 10 mA. The unit needs a minimum of 5 mA and max of 80 mA. The 4n25 data sheet says 1.15 V typical, I used 1.2, and a 1.5V max.

 

[colin55]

Connect TRIG- to the 0v rail and TRIG+ to any voltage that is between 4v and 12v. The timer will trigger when the voltage rises to about 3.5v.

 

[KeepItSimpleStupid]

I believe Ron's calculation would result in something a bit flaky or a marginal design. In other words, it may or may not work and doesn't give any margin of safety for aging and component tolerances.

The data sheet uses a typical operating current of 20 mA and Vr (max of 1.5). This is what I would use if I were doing a "Worst case" design which I didn't do, but I did consult the datasheet.

 

[Airman1]

Thanks for your replies

I am a little confused so will an 800 ohm resistor do the trick?

Or from Collins post can it be triggered with 5volts without changing any components?

 

[colin55]

It can be triggered with 5volts without changing any components.

 

[Airman1]

Ok Great thanks Colin

Has anyone had any experience with this timer kit?

From my understanding of the timer modes, Mode 2 will work for my project however does anyone know when the trigger is reapplied whilst the timing cycle has already started the timer will reset to zero but does it change the state of the relay when this happens?

I.e. the relay opens or closes?

Thanks again guys this forum has been a great help

 

[KeepItSimpleStupid]

Colin55: Read the article. The minimum trigger voltage is 6 V.

Airman1: 800 might work. 390 ohms is available in 5% tolerance and that in my opinion would be a better choice. My design was for 10 mA at 5V with a 380 ohm 1/2 W resistor for R1. With 390 ohms it will be slightly less.

I guess we didn't ask the other major question: How much current at 5V do you have available? I know you said 5V so I want to make sure it is 5V and not an open collector output of some sort. If it's 5V supplied by a contact closure or direct from 5V, were good.

 

[Airman1]

I saw the 6v as a min! So I definitely need to change the resistor.

It is 5VDC driven from a source, I have no idea what the current would be but it will be very small at a guess 100ma at the max. It’s just a Pulse & it is coming from an arcade gaming machine coin mechanism.

 

[Boncuk]

Hi Airman1,

mode2 is the only mode of operation which requires a momentary trigger signal. In all other cases the timer stops (pauses) when the trigger signal is lost and continues after the trigger signal is re-applied.

According to the specifications (see attachment) a minimum trigger current of 5mA is necessary. Using a 5VDC trigger signal I suggest to reduce the current limiting resistor R1(1K) to 680Ω resulting in a trigger current of 5.59mA. Since the maximum trigger current is 80mA applying a 12V trigger signal the current will increase to 15.88mA and remain within safe limits.

Triggering the circuit in mode2 when the timer has been activated resets the timer and restarts a full timing cycle.

The relay is connected with all three terminals which means you can use it as NC or NO relay depending on the connections you make.

Boncuk

 

[KeepItSimpleStupid]

Coin mechanisms can have relay and transistor outputs.

If it has a transistor output then you have to add another 0.6 V to the calculation: (5-(1.2+0.6))/20e-3 ohms. A transistor output would be an open collector output and it usually pulls to ground.

 

[Airman1]

It’s definitely not a relay output, so I guess it must be a transistor output then. Is there anyway to tell if i dont have the cct diagrams?

So if we look at Boncuk’s post if I use something just a little bigger than 680 ohms it should hopefully work.

Boncuks thanks for the info , i understand the operation of Mode 2 I am just not 100% sure if when the trigger is reapplied and the timer resets to 0 will the contacts of the relay remain in the same state prior to the trigger being reapplied during the timing cycle.

For example if the timer is already active and timing & the unit receives another trigger input will the relay open or stay in the same state ?

 

[KeepItSimpleStupid]

Smaller if it's a transistor output. (5-(1.2+0.6))/10e-3 evaluates to 320 ohms using 10 mA

I know, the resistors are all over the map.

If you go to the author's website, all the timing modes are explained. The author has all the datasheets for the parts there too.

 

[colin55]

I have used the optocoupler in my alarm circuit.
It works on less than 5v and requires 1-2mA input for a 1mA load

 

[Boncuk]

It’s definitely not a relay output, so I guess it must be a transistor output then. Is there anyway to tell if i dont have the cct diagrams?

It's definitely a relay output!

Take a close look at RLY1 and every terminal of Con2 to decide what it is!

So if we look at Boncuk’s post if I use something just a little bigger than 680 ohms it should hopefully work.

Go ahead and find a resistor just having a "little bigger" value than that I posted - probably 690 or 700Ω?

Boncuks thanks for the info , i understand the operation of Mode 2 I am just not 100% sure if when the trigger is reapplied and the timer resets to 0 will the contacts of the relay remain in the same state prior to the trigger being reapplied during the timing cycle.

For example if the timer is already active and timing & the unit receives another trigger input will the relay open or stay in the same state ?

It was clearly said that the timer will restart from zero if it is retriggered before it times out.

Furthermore I guess you don't require any more assistance since you seem to know everything better than the members trying to help you.

The circuit output is definitely a RELAY!

Boncuk

 

[Airman1]

Bonuk
You obviously haven't read the last couple of posts .
When I was referring to the relay or transistor output we were discussing the coin mechanism in an arcade machine, not the timer. Read the last couple of posts carefully before you post.

 

[Boncuk]

Bonuk
You obviously haven't read the last couple of posts .
When I was referring to the relay or transistor output we were discussing the coin mechanism in an arcade machine, not the timer. Read the last couple of posts carefully before you post.

Hi Airman1,

that's definitely the best way to discourage (p. them off) any member to answer your posts.

There is a minor difference between input and output!

The output of your arcade machine is an input for your timer circuit! which has been discussed already

So if your arcade machine uses a relay you should connect +5V to the positive triggered input of the timer with it's circuit ground connected to the negative trigger input of the timer. If it has an open collector output (the arcade machine) connect it to the negative trigger input of the timer, having +5V connected steadily to the positive trigger input.

If you don't name the "terminus technicus" properly you haven't understood a bit about electronics!

Failing to understand the problem is not anybody else's fault but only yours!

I allow any person to spit into my soup only once. Thereafter that person has to empty the plate!

Boncuk

P.S. My name is "Boncuk", not "Bonuk!"