Need electronic expert advice for a project

Tell us about your other hobbies & none QL related items here :)
User avatar
Pr0f
Gold Card
Posts: 287
Joined: Thu Oct 12, 2017 9:54 am

Re: Need electronic expert advice for a project

Postby Pr0f » Thu Jun 07, 2018 10:28 pm

This makes more sense now on the switch side of things.

The switch enable will trigger that lower of the 3 comparator's (there are 4 in the 339 package), and that in turn will switch Q6 on, allowing the SW pin to rise towards +12V, it would normally be dragged to 0.6V by the bias resistor to -12V and the action of the lower protection diode on the SW input, the 2 diodes here normally just pass any unsavoury voltage spikes to ground or +12V line.

So when enabled, the SW input will have a nominal positive voltage, but at rest -0.6V

The remaining 2 comparators in the circuit act as a window comparator, providing some hysteresis for the switch action, and toggling the JK flip flop.


FrancoisLanciault
ROM Dongle
Posts: 39
Joined: Mon Aug 08, 2011 11:08 pm

Re: Need electronic expert advice for a project

Postby FrancoisLanciault » Thu Jun 07, 2018 10:57 pm

Pr0f wrote:This makes more sense now on the switch side of things.

The switch enable will trigger that lower of the 3 comparator's (there are 4 in the 339 package), and that in turn will switch Q6 on, allowing the SW pin to rise towards +12V, it would normally be dragged to 0.6V by the bias resistor to -12V and the action of the lower protection diode on the SW input, the 2 diodes here normally just pass any unsavoury voltage spikes to ground or +12V line.

So when enabled, the SW input will have a nominal positive voltage, but at rest -0.6V

The remaining 2 comparators in the circuit act as a window comparator, providing some hysteresis for the switch action, and toggling the JK flip flop.


Well I am not sure I understand everything, but I am glad you do!

In light of these latest information, what is the good orientation of the Q7 transistor ?

Once the Q7 transistor orientation is clarified, I will built and test the light pen. Obviously I will report the outcome here!

Thank you again.

François


User avatar
1024MAK
Super Gold Card
Posts: 518
Joined: Sun Dec 11, 2011 1:16 am
Location: Looking forward to summer in Somerset, UK...

Re: Need electronic expert advice for a project

Postby 1024MAK » Thu Jun 07, 2018 11:27 pm

FrancoisLanciault wrote:
Pr0f wrote:This makes more sense now on the switch side of things.

The switch enable will trigger that lower of the 3 comparator's (there are 4 in the 339 package), and that in turn will switch Q6 on, allowing the SW pin to rise towards +12V, it would normally be dragged to 0.6V by the bias resistor to -12V and the action of the lower protection diode on the SW input, the 2 diodes here normally just pass any unsavoury voltage spikes to ground or +12V line.

So when enabled, the SW input will have a nominal positive voltage, but at rest -0.6V

The remaining 2 comparators in the circuit act as a window comparator, providing some hysteresis for the switch action, and toggling the JK flip flop.


Well I am not sure I understand everything, but I am glad you do!

In light of these latest information, what is the good orientation of the Q7 transistor ?

Once the Q7 transistor orientation is clarified, I will built and test the light pen. Obviously I will report the outcome here!

Thank you again.

François

Emitter goes to GND.

Mark


QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
User avatar
Pr0f
Gold Card
Posts: 287
Joined: Thu Oct 12, 2017 9:54 am

Re: Need electronic expert advice for a project

Postby Pr0f » Fri Jun 08, 2018 11:12 am

1024MAK wrote:
FrancoisLanciault wrote:
Pr0f wrote:This makes more sense now on the switch side of things.

The switch enable will trigger that lower of the 3 comparator's (there are 4 in the 339 package), and that in turn will switch Q6 on, allowing the SW pin to rise towards +12V, it would normally be dragged to 0.6V by the bias resistor to -12V and the action of the lower protection diode on the SW input, the 2 diodes here normally just pass any unsavoury voltage spikes to ground or +12V line.

So when enabled, the SW input will have a nominal positive voltage, but at rest -0.6V

The remaining 2 comparators in the circuit act as a window comparator, providing some hysteresis for the switch action, and toggling the JK flip flop.


Well I am not sure I understand everything, but I am glad you do!

In light of these latest information, what is the good orientation of the Q7 transistor ?

Once the Q7 transistor orientation is clarified, I will built and test the light pen. Obviously I will report the outcome here!

Thank you again.

François

Emitter goes to GND.

Mark


What he said :-)



Return to “The Off-Topic Section”

Who is online

Users browsing this forum: No registered users and 1 guest