Turning on a TIP35C Transistor from a CD4017 IC

JimB · Jul 4, 2020

Beewild said:
Your thoughts please!

Please draw transistor symbols correctly using the standard symbols.
Having to interpret your home made symbols is annoying.

JimB

gophert · Jul 4, 2020

Beewild said:
Ok, have decided to go back to the idea of transistors. Attached is my completed circuit. Your thoughts please!

it is worth doing the experiment. Either it will work as you want or you will learn something as you troubleshoot,, test, redesign snd try again.
Best of all, there is very little risk if the design doesn't work (I.e. you're not going to hurt yourself or others and it won't burn your house down) so don't let other people convince you not to try it.

Good luck.

gophert · Jul 4, 2020

JimB said:
Please draw transistor symbols correctly using the standard symbols.
Having to interpret your home made symbols is annoying.

JimB

that's his perf-board layout. It's fine.

JimB · Jul 4, 2020

gophert said:
that's his perf-board layout. It's fine.

OK. But what he said was:

Beewild said:
Attached is my completed circuit.

When it would have been more informative to say:

Attached is my completed perf-board layout

JimB

gophert · Jul 4, 2020

JimB said:
OK. But what he said was:

When it would have been more informative to say:

JimB

Yeah, but I'm in a forgiving mood because today is the great American Holiday - the day we celebrate by feeling sorry for a local kid who burns, mutilates or blinds himself or unintentionally (or intentionally) sets something ablaze.

im surprised you're not in a better mood, today's the day pubs reopen and you get to drink a pint through a mask.

audioguru · Jul 4, 2020

There is so much voltage loss that there is not enough voltage to turn on three 3.6V blue LEDs.
The TIP35 will get VERY hot (it will need a pretty big heatsink) and the 2nd BC337 will get hot but will be fine:

JimB · Jul 4, 2020

gophert said:
Yeah, but I'm in a forgiving mood because today is the great American Holiday - the day we celebrate by feeling sorry for a local kid who burns, mutilates or blinds himself or unintentionally (or intentionally) sets something ablaze.

Spoken like a true cynic, a man after my own heart.

gophert said:
im surprised you're not in a better mood, today's the day pubs reopen and you get to drink a pint through a mask.

Indeed they do, in England.
However I am located in Scotland where the pubs are not yet scheduled to open.
But thank you for the suggestion, in the fridge I have a nice cool bottle of beer which will go down a treat in a few minutes.

Oh, before I forget, happy 4th July. You were well rid of us.

JimB

Nigel Goodwin · Jul 4, 2020

JimB said:
Spoken like a true cynic, a man after my own heart.

Indeed they do, in England.
However I am located in Scotland where the pubs are not yet scheduled to open.

Yep, pubs are open - but I don't have the slightest inclination to go and visit one

I did hear from a lady today though, she was stuck in traffic due to idiots queuing to try and get to the Tupton Tap in the middle of this map:

Google Maps

Find local businesses, view maps and get driving directions in Google Maps.

www.google.com

Considering the car park is full of tables for social distancing, not surprising they couldn't get in.

Beewild · Jul 4, 2020

Nigel Goodwin said:
I'll say again, as I did in the previous similar thread, it's very poor to use a darlington in that way, as there's very little collector voltage on the BC337 collectors, and thus little current to drive the TIP35. It's FAR better to drive the BC337 collectors from the higher supply rails.

Even better, as there's three transistors, is to make the middle one PNP, fed from the collector of the first one, both of course powered directly from the supply rail - maximising base current for the TIP35.

Or, as you say, use a suitable MOSFET.

Forgive my ignorance. Below I have drawn what I think you mean and have changed the resistor to the base of the first npn from 10k to 1.2k.

audioguru · Jul 4, 2020

Using ordinary transistors providing a massive 8A of current when driven from a weak Cmos CD4017 you need the circuit to be like this:
EDIT; Driver transistor is a PNP BD140.

Beewild · Jul 5, 2020

Thank you for your clarification and details for the circuit. I am an electrician in New Zealand so more used to 230vac or 3phase. My electronics kniwledge is quite limited but something I do find interesting.

Nigel Goodwin · Jul 5, 2020

Beewild said:
Forgive my ignorance. Below I have drawn what I think you mean and have changed the resistor to the base of the first npn from 10k to 1.2k.

This was my thought, which allows full current drive adjustment in each transistor:

Resistor values can be tweaked accordingly.

Needless to say, R5 shouldn't be 1K

ronsimpson · Jul 5, 2020

Nigel Goodwin · Jul 5, 2020

ronsimpson said:
View attachment 125778

Presumably you've not read the rest of thread?.

audioguru · Jul 5, 2020

I corrected my schematic to show a BD140 PNP.

Nigel Goodwin · Jul 5, 2020

audioguru said:
I corrected my schematic to show a BD140 PNP.

Oops - and I blindly copied your transistor numbers!

Beewild · Jul 5, 2020

I had noticed your pnp was labelled bd139 instead of bd140. I have used both previously.

Beewild · Jul 5, 2020

ronsimpson said:
View attachment 125778

Would it not be better to drive the mosfet fom the small trabsisor? Also mroblem being easy access to a low impedence mosfet.

Beewild · Jul 5, 2020

ronsimpson said:
View attachment 125778

OK I have managed to find a supplier for the IRFP3206PBF mosfet. So lets start again. 10k between the 4017 and the mosfet?

gophert · Jul 6, 2020

Beewild said:
OK I have managed to find a supplier for the IRFP3206PBF mosfet. So lets start again. 10k between the 4017 and the mosfet?

no, you can use much smaller value resistor from CD4017 to gate. Like 1000 ohm for your slow switching speed. But use a 10k to 100k (any sizein between) from gate to ground).

note: the Mosfet gate is essentially a 1nF capacitor that you are charging, no continuous current flow like your other transistor..

Turning on a TIP35C Transistor from a CD4017 IC

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