R1 is 15 ohms.

The 0805 is a size code for surface mount components. If you are using through hole, you can ignore the 0805.

If you want to replace Q1 with a relay, you need to be sure that the relay coil's current requirement won't stress the MCP1416.

ETA: I don't think the MCP1416 is available as a through hole component, i.e., surface mount only.

 

Thanks, Im going to keep Q1 with the 90% duty cycle from the 555 I dont think a realy is a good idea, or ? I will put a 40amp on the main switch, I was just thinking about, if poss changing SW1 to a SPST ?

Thanks Again

 

Thanks, Im going to keep Q1 with the 90% duty cycle from the 555 I dont think a realy is a good idea, or ? I will put a 40amp on the main switch, I was just thinking about, if poss changing SW1 to a SPST ?

Thanks Again

Sorry, I didn't read your post closely enough. I don't know about changing the switch, because I have never used an MC14541.

 

Thanks, no problem. Does anyone know what the value of C6 is please

Thanks

 

Thanks, no problem. Does anyone know what the value of C6 is please

Thanks

C6, together with R3 and R4 determine the timing of the 555. If you want the same time as you originally did, use the same values I gave you earlier.

 

Yes, sorry with you now Ive just worked that out as you posted, another question, sorry, on the curcuit there are 2 extra's C2 & C4, Ive not got them on my 555, what do they do ?

Thanks

 

They are filter capacitors to keep power line noise from affecting the 555.

 

R1 is just 15 ohms. The ones marked 0805 should be the values people have already helped you with. Putting a SPST in the place of the button should be fine.

 

R1 is just 15 ohms. The ones marked 0805 should be the values people have already helped you with. Putting a SPST in the place of the button should be fine.

It's your circuit, but I am curious why the MC1416 is needed. The output from a 555 seems perfectly adequate to provide gate voltage for the MOSFET. I must be missing something; what is it?

 

Can I put a LED on pin 8 of the MC14541 as well so I know when the timer had stopped or is it best to put it somehwere else ?

Thanks

 

The pwm frequency might be slow enough that no MC1416 is neede. I haven't tested the circuit. The main thing is can the 555 timer's 0.2A output turn the MOSFET on and off fast enough to prevent it from getting hot.

Looking at the 14541 data sheet it can easily drive a LED.

 

Since my last post I have built the 14541 part of the circuit. There is one thing about it that I forgot: on power up it resets itself and starts the timer as if you have pressed the reset button.

In any case, with a 0.047 uF capacitor it runs for about 3 1/2 minutes and with a 0.1 uF cap it runs for 7 1/2 minutes so a 0.068 uF cap should be pretty much 5 minutes.

 

Thanks again for the info, are all capacitor that are listed in the circuit uF ? just doing a goole search I see there are uF, nF and pF

Thanks

 

They are all uF.

 

One more thing to be aware of is that its output goes high as soon as you take MR high but it does not start counting until MR goes low again. So it will let the 555 run for 5 minutes plus however long MR stays high.

Is this and the fact that it runs once at power up a problem?

 

One more thing to be aware of is that its output goes high as soon as you take MR high but it does not start counting until MR goes low again. So it will let the 555 run for 5 minutes plus however long MR stays high.

Is this and the fact that it runs once at power up a problem?

Thanks again, I think im getting this if I put a SPST as SW1 it will run for 5 mins then time out or would it re-start because SW1 is closed.
Running once at power up is perfect

Thanks

 

HELP, Ive got all me components, Ive just started with soldering the MC14541 to the stripboard, I worked down from pin 1 and then realised the MCP14541 is a 14 pin, the 14 pin chip on the circuit is only, if you count the pins a 12 pin as #4 & #11 is missing, are they missing becuse they are not used or am I overlooking something

Thanks

 

You're not overlooking anything don't worry. Usually if a pin is missing from a circuit diagram it just means it isn't used... NC (no connection). A quick look at page 2 of the datasheet shows this on the pin-out for the IC: MC14541 Datasheet - pg2

 

Im just waiting for mosfet and driver, Ive done the rest but have a small problem. when I connect power it starts straight away, after the 5 min time it will start again when I connect pin 6 of the MC14541 to feed, Is there anyway to make it start only when pin 6 (SW1) is connected

Thanks

 

I don't think there is any way to prevent it from running once at power-up unless you hang some other logic around it to disable the output for that first time only.

What do you mean by "connect pin 6 .. to feed" ? How exactly are you using pin 6?