Homebrew PCBs

On Tue, 10 Feb 2004 21:19:48 -0600, Esteban Arias <earias@...> 
wrote:

> Thanks Stefan for the schematic. Now I have a good idea over the circuit.
>
> Today I search in my house and find the main board of the printer. I 
> review
> the pcb and find the components asocciates to the fuser; BCR8PM a 8A, 
> 600V
> triac. I think use the same triac for driver the fuser but with your 
> circuit.
>
> The service manual say over the internal thermistor: "TH901". I think it 
> is
> a 10 K thermistor. it is ok for your circuit ?
>
> Thanks,
>
> Esteban Arias
> earias@...
>

hi,

10k thermistor is well posible.

you want to use a triac, this needs to be triggered.


it will work with my circuit but would need 1 more component.

You can't connect the triac to my circuit without isolation.
The temperature sensor in the fuser is not isolated for 220V you may
damage the sensor and endanger yourself.

The common procedure would be to use a optocoupler.

(this is the same as in my solid state relais. it is just
a optocoupler and a triac.)

There are Triac optocouplers (consisting of a light-sensitive triac and a 
diode).
these are nice for such applications. (but any other optosiolator will do).

Tell me what you have at hand, i think the HP printer triggers the triac 
with a opto
too so this will not be a problem.

If you need help with a circuit tell me which parts you have.

The printer has powered the fuser - so it must contain all components you 
need
(spare the potentiometer). No need to go shopping i think.



ST