Problem with k8035 internal oscillator

I bought today the velleman kit k8035 its everything ok with the functions except the internal oscillator dont work.

I put the “dip switch” nº 1,2,4 ON (50.59) and the value dont decrease alone with internal oscillator.

The contact of dip switch its ok and when I put only nº4 ON appears error nº3. I think this function its correct.

I done everything correctly as the manual and I think the problem its the program of pic16c57.

I look for a word from you.

Best regards,

Nélio Simões (Portugal)

The counter will only start to count down, while the “count down input” (pin8) is active (with external switch).

Err3 error is normal when you only set SW4 to ON.

hello! ok with the external switch the value decrease, but what is the funcion of the internal oscillator?
with the internal oscillator the value dont decrease alone?

best regards

I just told you, no.
The counter will only count up/down, while the “count input” is active (with external switch).
The purpose is measuring the time wish is the external contact is closed.

If you haven’t such input, this counter is useless, than you can use also a simple watch.

ok! thank you.

best regards

Sorry to insist, but on page 2, Features & Specifications, it says has one of the features: An internal oscillator allows time measurement.
Does this means, that if a certain contact is established by the K8035, it starts count, UP or DOWN, second after second, like a time counter?

If not, I am looking for a time counter, to count elapsed time during a Pit Stop (F1 wheel change). After START signal (pushing a button), the clock will start to count in seconds measurement and, when the person finishes it, pushing another or same button, the clock stops and shows elapsed time.

Perfect would be a clock with mm:ss,sss but, I would take an mm:ss configuration.

Can you please help? I have already purchased the K8035, it’s running and working fine, except I cannot find the “Time measurement” as stated in the Instruction Manual.

Best regards,


I have just built the K8035 and wished to use it as a timer. The instructions are not very clear and the comment from Vellman earlier ‘to use a watch’ was not helpful.

To count time, apart from SW4 being on, pin 9 on the external connector needs to be connected to +5v after initialisation.


Set the switches as stated in the manual.

To count up tie pin 9 to pin 7
To count down tie pin 8 to pin 7

Hope this helps.

Hello group the k8035 up:down counter works as intended. Just a question. Can anyone explain the function of D7 in the L.E.D part of the circuit

Hello @scron724 ,

D7 is a protection diode. This diode serves to protect the PNP transistor T5.
This if you would connect a relay to the output terminal no. 5 and 4 of connector SK1.
(see page 9 fig. 1.0 & 2.0 for illustration, so you don’t need to add extra diode over the coil of relay)

Best Regards,
Velleman Support