Dew controller

[rockystar]

I've eventually managed to get round to v2 of a dew controller,  after I blew the first one up!

I have checked with a volt metre and power is running all the way through the system to the phono plugs, but the strap doesn't seem to be heating up. Do the phono plugs need grounding?

[wetwalker]

Short answer yes one side through a series of resistors.

Ian

[rockystar]

Yeah,  been thinking I need to complete the circuit,  but it isn't obvious how I wire up the negative on the phono plug... ?

[Gina]

The outer shell is generally used as the return or negative.  This is used as the screen/ground on audio circuits for which they were designed I believe.

[PaulR1]

Ive often wondered about the need for a dew controller :

first time out with my new guidescope it dewed up , so I 3D printed a tube to fit over the end . No more dew

So are these dew controller/heaters really needed ?

[rockystar]

3 minutes ago, PaulR1 said:

Ive often wondered about the need for a dew controller :

first time out with my new guidescope it dewed up , so I 3D printed a tube to fit over the end . No more dew

So are these dew controller/heaters really needed ?

It's to power an Eyepiece dew strap - on a few occasions I've had sessions cut short as the eyepiece has steamed up and I've struggled to keep them clear for more than 30 seconds or so before they steam up again.  Hoping it will enable me to prolong the session. 

 

[PaulR1]

ahh ok ... then my tube idea wont work for you

[rockystar]

8 minutes ago, Gina said:

The outer shell is generally used as the return or negative.  This is used as the screen/ground on audio circuits for which they were designed I believe.

So can I feed the negative onto a ring and loop it before the nut? That should then be hooked up to the outer shell? 

[rockystar]

Just now, PaulR1 said:

ahh ok ... then my tube idea wont work for you

I've got a reflector,  so don't normally have an issue with the primary mirror.  I've got a homemade dew shield to help with the secondary, so already implementing your tube idea

[Gina]

3 minutes ago, rockystar said:

So can I feed the negative onto a ring and loop it before the nut? That should then be hooked up to the outer shell? 

Yes, that's how I've done it in the past where I haven't got a big solder tag for it.

[rockystar]

It's working

minor issue inn that my original idea for a power source isn't generating enough,  but given a different power source,  the controller is now working. 

[Gina]

Great.

[cjdawson]

On 27/08/2018 at 20:43, PaulR1 said:

Ive often wondered about the need for a dew controller :

first time out with my new guidescope it dewed up , so I 3D printed a tube to fit over the end . No more dew

So are these dew controller/heaters really needed ?

Dew heaters can be used in several places.

 

I have two on my scope.

One on the main optics and the other on the guide scope.    Both of these have dew shields.  The combination of the heater and shield means that I can have all night sessions without any problems.  Without the heater, after a few hours the main optics will dew up and I'd have to cut the session short.

Please note, my main scope is an SCT and my guide scope is a refractor.   Both of these have optics at the end, which are the things that dew up.   Newtonian scopes are less prone to is as the main tube acts as a really long shield.   however, it's still possible for them to dew up hence some people making devices to keep the dew away.