Home made dew controller

[davieradio]

Hi Guys I 've just finished making a dew controller from a vellerman kit . I was a dc motor control kit that used pulse width and variable pulses .

It is Kit K8004 you only have to change the capacitor C3 to about 10 micro farad

It will give about 3 amps out , and if you take the puses out of pin 11 on the main chip to a tip 43 trany you can have an aux output for eyepieces

now all I need to do is make up the heaters, I've got some resistance wire from an old storage heater and will experiment with that.

Dave

[radioactive]

nice one Dave yes the wire from a storage heater will be pretty much ideal Id say

[George]

Nice

Any piccys and instructions on how you built it?

[davieradio]

picture of dew heater homemade

[davieradio]

center]

(click to enlarge)

[plasma.d00d]

Nice

Any piccys and instructions on how you built it?

http://www.aozc64.dsl.pipex.com/tips/dewheater.htm

[davieradio]

Yes thats the same Kit , mine is built into a Maplin box and slides in sideways, using the grooves in the box.

have used one of the output pins to feed another transistor on a seperate heatsink which gives an AUX output (smaller) for eyepieces and finders ,the red led flashes then the green, all works fine

Another mod is to be done increase the inductance of the filter slightly to eliminate the switching interference at the 12v input which will get on the power line line

Dave

[anthony]

Sterling job. I am envious of your know how with the electronic stuff.

Anthony

[daz]

Another mod is to be done increase the inductance of the filter slightly to eliminate the switching interference at the 12v input which will get on the power line line

Can someone translate??

Looks a great job there guys!

[Beyond_Vision]

There is most likely to be an input filter on the circuits DC input. The purpose of the filter is to reduce electrical noise from being transmitted back up the supply wiring. This noise could interfere with other electronic equipment e.g CCD cameras etc. The filtering circuit that was originally in place may not be man enough to filter the noise so could need modifying.

To be honest with you if you were going to cut out EMC properly you should have a metal enclosure or plastic box with a metalised inner surface to reduce radio frequency interference. The box should be connected to 0V of the circuit. The output to the heaters should also be filtered to reduce noise.

By the time you have bought the Vellerman Kit a Metal Box and factored the time spent building it and adding proper filtering you will be close to the price of a four channel controller for £50-£60 which has passed EMC regulations.

Where you may save money is in making the heater bands yourself

Despite all my comments Daveiradio you have produced a nice looking box I hope it works ok.

[davieradio]

Why bother......Well I like making things and getting them to work.

In my defence, I don't like using metal boxes because of the condensation the can appear inside the box.

On screening for RFI and EMC Use screened leads, a filter in the DC input which will cost next to nothing 2 capacitors ana small inductance.

I cannie grind a mirror but this is summat I can do my self and enjoy ...whats more I learn from my mistakes that go along the way

Now If I could build a clear skies machine that would be triumph!

[Sam]

Put me down for one of the clear skies machines!

[Beyond_Vision]

Why bother......Well I like making things and getting them to work.

In my defence, I don't like using metal boxes because of the condensation the can appear inside the box.

On screening for RFI and EMC Use screened leads, a filter in the DC input which will cost next to nothing 2 capacitors ana small inductance.

I cannie grind a mirror but this is summat I can do my self and enjoy ...whats more I learn from my mistakes that go along the way

Now If I could build a clear skies machine that would be triumph!

Sorry davieradio not criticising what you have done and yes it is enjoyable making stuff yourself as I have done often being an Electronics Engineer. The end result looks pretty good and Im sure will work ok. All I was saying that you have to consider EMC/EMI aspects of switching current at high frequencies especially if you are imaging.

Regards

Kevin