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### Topic: dimming neon (not fluorescent) (Read 2085 times)previous topic - next topic

#### fubbi

##### Apr 11, 2012, 02:15 pmLast Edit: Apr 11, 2012, 02:17 pm by fubbi Reason: 1
Hi

I want to do some fast dimming of a neon (real neon, not fluorescent) sculpture. I'd like to do various fast patterns and random switching.

The ballast I am getting is the 6th from the top called "9.000":

It has a 0-10v dim input. Can I just take a 10k digital pot and dim away? Are digital pots fast enough for "switching" as well?

Thanks

fubbi

#### DVDdoug

#1
##### Apr 11, 2012, 09:09 pm
Quote
It has a 0-10v dim input. Can I just take a 10k digital pot and dim away?
Probably...   But, it would be helpful to know the input impedance (or current).

For example, if the input impedance (of the dimmer circuit) is 1K and you use a 10k pot, the voltage won't be linear (you'll get around 2V at the mid-point, instead of 5V).   To some extent, you can compensate for non-linearity in the software if necessary.

And, if the impedeance is really low (very unlikely) you can get excess current through the pot, and damage it.

It wouldn't hurt to try with a regular analog pot.   Worst case you fry the pot, but that's very unlikely.

Quote
Are digital pots fast enough for "switching" as well?
Probably...  What frequency are we talking about?    You can check the specs, but I assume they work at audio frtquencies (beyond 20khz).

#### fubbi

#2
##### Apr 12, 2012, 03:50 pm

Update: The input of the ballast is not for a variable resistor but for PWM 1-10v

can I use a simple circuit like this:

and will the 0-10v cause problems when the ballast expects 1-10v?

thank you

fubbi

#### widgetmaker

#3
##### Apr 12, 2012, 04:03 pm
Digital pots tend to be very fast, fast enough that your eyes wouldn't be able to respond as quickly as they can switch.  It's unclear what the input requirements are for your selected dimmer; I could find the information easily from the site you listed.  My guess is that the input to the dimmer is high impedance (as in a MOSFET gate), and that the NPN controller you showed a scematic for would be just fine if all you want to do is switch on and off.  You could also use a MOSFET for the transistor and virtually elimate the load from the Arduino (presumably the source of your 0-5V pulse).

#### fubbi

#4
##### Apr 12, 2012, 04:07 pm

Digital pots tend to be very fast, fast enough that your eyes wouldn't be able to respond as quickly as they can switch.  It's unclear what the input requirements are for your selected dimmer; I could find the information easily from the site you listed.  My guess is that the input to the dimmer is high impedance (as in a MOSFET gate), and that the NPN controller you showed a scematic for would be just fine if all you want to do is switch on and off.  You could also use a MOSFET for the transistor and virtually elimate the load from the Arduino (presumably the source of your 0-5V pulse).

thank you

fubbi

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