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Design Help Needed

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hi shermaine,

Len has shown 4K7 resistors on his latest posted drawing.

You can use 1K0, if you have no 4K7's.
 
shermaine said:
Hi,

Thanks for your reply again. Do i hv to use ur resistance value? Or can i use 1Kohm?
You can use whatever you have in the range 1k to 6k8.

I chose 4k7 since it gives a current of 1 mA which is all you need to wet the switch contacts.

1k means a current of 5 mA which is acceptable but it does not need to be that high.
 
i was wondering if there is any software out there that you can try out the schematic layout and see the waveform 1st? is there any freeware?
 
hi shermaine,

Some sim software will require a learning period before you can use it on this circuit.
I would suggest you get a 'plug' type project board and just build it as a prototype, it will be quicker.
 
test the circuit is sections. Leave the counter out and test the gating first. Then insert the counter. You can see if it is counting by looking for pulses on QA.
 
Can i check with you all, for the pcb mount switch, there are 4 legs so i just connect any one point? And for the dip switch, i got 8 legs, that mean i just connect any 2 of the legs? Please advise. Thanks.
 
shermaine said:
Can i check with you all, for the pcb mount switch, there are 4 legs so i just connect any one point? And for the dip switch, i got 8 legs, that mean i just connect any 2 of the legs? Please advise. Thanks.
Do you have a multimeter?

If so, use it to measure the switches.

If not, buy or borrow one.

That is how I work out switch pins.
 
shermaine said:
Thanks! Btw, i need to connect all the clk to 555 timer. I'm not sure which pins i need to connect. Please advise
Do you have data sheets for all of the ICs?

You will find the pin numbers on them.
 
shermaine,

DIP 4 Bit Switch Layout, you should be able to work out the switch connection from the drawings.
 
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hi,

Thanks! i did download it.
There are points like Trigger,output,reset,discharge, threshold and contol voltage.
I was wondering which points i hv to connect the clock to? Please advise. Thanks.
 
There have been plenty of posts on the 555 in this forum and plenty of info available on the internet.

The clock signal can be taken from the output of course.
 
Hi guys,

Thanks so much for the reply. I have finished the wiring. I'm left with a 9V battery to test it out. Hopefully, things are going to be well! cheers!
 
shermaine said:
Hi guys,

Thanks so much for the reply. I have finished the wiring. I'm left with a 9V battery to test it out. Hopefully, things are going to be well! cheers!
Let us know who it goes.

If you use 9 Volt rather than 5 Volt, you will need to increase the LED resistors from 470 Ohm to 820 Ohm or 1k.
 
Hi Guys,

I have tried it out and it doesn't seem to work. I dont know why. Initally, i was using a 330ohm for the leds and i did change to a 998ohm. But it seem to hv the same problem too. I'm not sure if my dip switch connection got problem or what. I'm connecting the off row, pin 1 and pin 4 to a resistor before a VCC. When i tact on the push button switch, it doesn't seem to work either. It got no effect.
these are the ouput of the tact switch on the led.
(1) off off off off > red light up
(2) off off off on > green light up
(3) on off off off > red light up
(4) on off off on > green light up

the led light up without the tact on the pushbutton.
whe i tact the pushbutton, nothing happens. Can advise me what could be wrong? Please advise. Thanks!
 
Which circuit are you testing. I can only guess without a circuit.

Have you used a Multimeter to measure the voltages?

You should see a change in voltage when a switch is set. For example, in my last circuit, if S1 is closed the D0 voltage will change from 5 Volt to 0 Volt.
 
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hi,
I'm not sure if my dip switch connection got problem or what. I'm connecting the off row, pin 1 and pin 4 to a resistor before a VCC.

Look at the drawings.

Is this how you have connected the DIP Bit switch?

You MUST answer our questions, if we are to help you.
 
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Yes, we are not mind readers. We are spending our time trying to help you but you are not doing your part.

It is impossible to fully understand what you are saying in words. We need a diagram to look at so we can give specific answers.
 
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