dew heater problem

[a10ken]

Hi all

i just bought a second hand kendrick digi 7 and i want to know what the voltage output is at 100%. as i think one channel is dead.

thanks

a10ken

[Merlin66]

Without going out to the observatory I say it should be 12V.

What are you using to supply power to the controller? Could be you don't have enough Amps available??

[a10ken]

odessey battery, normaly cranks the harley over so should be ok

[Carbon Brush]

Dew heaters work by turning the 12V supply on/off at intervals. Some do this rapidly, some slowly. But for all the on/off ratio determines the power.

Depending on the manufacturer, you can get confusing results on a meter.

If the on/off cycling is very slow, you will see alternately 12V, 0V, 12V, 0V. But if the cycling is fast you will see a proportion of the 12V showing on the meter. However, if using a digital meter, it probably won't accruately read under these conditions.

A better method is to connect a small 12V bulb. For example car sidelight (5W), or interior light (5W or 10W). If you can wind the brightness up/down you have a fast cycling controller. If you see the bulb going on/off, you have a slow cycling controller.

In either case as long as you can change the bulb brightness, or on/off cycle, you have a working controller.

Hope this is useful, David.

[a10ken]

sounds good to me. off down the shed then!!

thanks dave.

[hemihaggis]

i would think a battery that turns over a big vtwin should work ,but i would rather use a more deep cycle battery , bike batterys are designed to give a big shove of current quickly, i think a longer slower cycle would run scopes and dew heaters better ,

[a10ken]

hi hemi

have a look on the odyssey web site. these are some of the best batt,s available

[hemihaggis]

hi hemi

have a look on the odyssey web site. these are some of the best batt,s available

yes im sure they are great batterys ,they are designed to churn out large burst of power for a few seconds to statt an engine then run off an alternator , but they are not deep cycle , deep cycle batteries are designed to give large amounts of power for a long duration with out being recharged , meaning you could probably run your scope for days on end with one !! the deep cycle battery in my winch has a cold crank power of 2000amps for 20 seconds your harley battery will provide around 400amps for 5 seconds , there is no comparison im afraid ,

so you are out in the middle of winter , running you scope.mount , dew heater / laptop / ect , off of a battery ,which one would oyu want ??

[a10ken]

point taken:icon_salut:

[faulksy]

as said some dew controlers use on/off switching called pwm (pulse width modulation) on max power should be the same as input power and reduce to around 5volts depending on the system. you say you think 1 channel is down cant you plug into another channel to iliminate this dodgy one.

[Adrian Condon]

Hi Ken,

I am the proud owner of a Kendrick Digifire 7.

I run mine in the field off a Maplin's 5-1 Battery Pack.... (not brilliant) I intend to upgrade to a Marine Battery at 110 amps. When funds become available.

In the meantime, using the Digifire 7 when there is a mains supply available, (back garden or at a Star Party) I use a Rapid 25Amp Converter Digital Display. 15v 25a Smps with Digital Display

If you happen to have one of these (or similiar) or a colleague who has one, you could easily check out each heating strip in turn on each of the 6 outputs. (4 of which are controllable).

Set the Voltage to 12 to 12.2 volts and the amperage used by each heating strip on each output channel will be displayed.

Check each strip in turn on every output channel.

If one of the outputs is dud then this method will find the dud channel. If a heater strips fails on every channel, then there is a problem with the heater strip.

The final test is to attach all the heater strips to the Digifire 7 and you will get the total amperage you are using.

Incidentally, my Dew-Not Telrad heater uses 0.4 amps.

The next test would be to lower the voltage on the converter to say 10 volts, the low voltage light on the Digifire should light up. This light is activated if the voltage drops below 11.8 volts.

Trust the above is helpful.

Cheers

Adrian