Help with a poorly looking component identification plea

[Techie_hobby1]

stj and all
Note: I am extremely novice at producing circuit diagrams at the moment, and trying to get to grips with KiCad, but this is how I think it is wired up....

I will only like kind replies please.

REMEBER We all had to start somewhere and with time they will improve.

[stj]

not bad.
i'm not a kicad fan untill they add "rubber banding",
till then i'll stick with Eagle - the good eagle before AutoDesk fucked with it!

[stj]

so the burned part is a resistor to drive the led from mains - ideally with only a couple of mA.
if the heater doesnt heat then it can only be the switch or thermal cutout - presuming the ptc isnt cracked inside.

[truclacicr]

Wow, that's a scary circuit.

[Techie_hobby1]

stj
Thank you for your response.

i'm not a kicad fan untill they add "rubber banding",

What is rubber banding?

so the burned part is a resistor to drive the led from mains - ideally with only a couple of mA.

Ahh okay, now I understand. I thought the 4.7k ohm resistor was used for current limiting the whole circuit but then that would be crazy, but of course now you explained it a little better I totally understand why this would be a resistor.

Question.. from my calculations using a 240k resistor to limit the mains current my calculations are as follows (please correct me if I wrong here):

mains (UK) = 240v
resistor = 240k ohm (240,000)
I = V / R
240
240,000 = 0.001 mA

With that in mind Watts is P = I x V
therefore

0.001 x 240 = 0.24

I will replace it with a 240k @ 0.5W resistor to ensure it does not get to toasty, but will probably replace the Diode just to be on the safe side.

[stj]

we are both wrong about the resistor calculation
your wrong because rectified mains is about 340v (240 x 1.41)
i'm wrong because it's only half-wave rectified - although the peak is the same.
maybe 330k

rubber banding is where you can grab a part or trace and move it and it stays connected and just stretches to the new location.
handy if you start running out of space as you can grab whole chunks of a circuit and move them apart without breaking the interconnections

[Techie_hobby1]

stj
This bit always confuses me.. 340v = rectified mains is this because of the diode (approx) 0.7v on both half cycles?

rubber banding is where you can grab a part or trace and move it and it stays connected and just stretches to the new location.

Okay I know what you mean by rubber banding now - I just called it footprint dragging haha. KiCAD started to include that feature back in version 8, and it has since been improved with this version 9.

So which components do I need to remove to make this a little safer. If I just disconnect the 12v DC port does that mean only 1 of the PTC heaters will function... if so I wonder if this will produce enough heat... this will definitely need to be corrected

[stj]

it only uses 1 ptc at a time.
the dc jack is the questionable part.

mains is a sinewave, the stated voltage is the average not the peak.

[Techie_hobby1]

Oh now I understand.. I thought that the 2 PTC's were connected in Series, but looking back at the schematic they are 2 separate circuits as per your previous mentions
Therefore, if I disconnect DC socket, 1 x ptc and the 3.4k resistor that will solve the danger side.

Any thoughts on adding some kind of temperature control i.e thermostat to control its temperature a little better.

[stj]

it will never go hotter, but it can go colder.
you need a pwm based temp controller module from aliexpress - if they make one.

you could also keep the dc jack but make it safe by seperating it.
use a 2pole switch and a second led.

[Techie_hobby1]

stj
Yes it would be to control temperature to make it a little colder. It does seem to get pretty hot - considering the size of the PTC it is quite impressive at what heat is produced.. so a way to turn the heat down a little bit, ensuring that it does not scold my friend would definitely be a good mod.

you need a pwm based temp controller module from aliexpress - if they make one.

Would something like this work PWM, Electronic Speed Controller Module - 240v

[stj]

it's overpriced.
and not that good - you ideally want something with a temperature sensor
maybe designed to drive a hot-air station?

[truclacicr]

If you decide to eliminate the DC side of the circuit, or separate it, could you use an ordinary incandescent light dimmer switch? It's not ideal, but it's cheap.

[Techie_hobby1]

truclacicr
I will definitely be eliminating the DC side..
I didn't think the incandescent dimmers used PWM? however the LED dimmer modules worked as PWM from memory.. Iactually think I might have a few of those in my spare parts storage, therefore even cheaper still.
Surely they would work because they are built for 240v??

[truclacicr]

Incandescent dimmers control a TRIAC by varying the phase angle.

https://www.electronics-tutorials.ws...08/power27.gif

[stj]

the problem without feedback is the ptc will ajust itself to fight the dimmer

[sam_sam_sam]

the problem without feedback is the ptc will ajust itself to fight the dimmer

To a certain extent this is true however you would have lower heat output overall which would indirectly control temperature plus depending on how much power is being delivered to the heating element it still might not make it linear enough to be practical in the long run

[Techie_hobby1]

How about Arduino or something like that. Anyone know if this is possible to overcome the obstacles that keep getting in my way?

[stj]

arduino would still need a triac circuit and a thermocouple

[Techie_hobby1]

Would this work?
220V AC TRIAC PID temperature termocouple