Dahua HFW-1831 stuck IR cut filter

M

MakeItRain

Pulling my weight
Aug 7, 2017
418
225
Hi everyone

I got a HFW-1831 bullet with a stuck IR cut filter. All the trees and grass turn cyan purple during the day. At night time it is fine. Other than that the camera runs fine.

I was able to dis-assemble the lens head which is two screws bolted to a PCB. Then the IR cut filter mechanism is one screw.

The first thing I see is nothing wrong visually with the IR cut filter. I can see through it. The second thing is, since I do not know what is wrong, I put it all back together and now my camera is slightly more blurry in the background (far distance). For close distance 3-10 ft. the image is sharp and fine.
Did I mess up the tuning of the fixed-focus lens?

Thanks


IMG_2272.JPG
 
You changed the focus somehow, you didn't get it back exactly as it once was.
A rap with a screw driver handle on the cam, can usually unstick the cut filter.
 
Is it safe to wipe isopropyl 70% alcohol on the lens and filter? or just compressed air?

I will take it apart once again and mess around with it some more.

TIA
 
the picture you showed of the IR cut filter mechanism has the filter withdrawn (not deployed),
which is why it's clear. During the day, the filter SHOULD be deployed and appear pinkish/purple,
blocking IR from giving the daytime image that pinkish/purple hue.

You might try applying voltage to the filter mechanism and see if the filter 'snaps' into place.
It might require only 5V, tho so be careful.

If it's indeed dead, should be able to find a replacement here somewhere:
Buy ir cut filter and get free shipping on AliExpress.com

and yes, the mechanism was probably shifted somewhat on re-assembly, causing your out-of-focus.
Re-focus by twisting the lens in the holder. probably need to scrape away the glue used by manufacturer to fix lens at first assembly. I use the tip of an Xacto-type blade for that. Avoid solvents here. re-apply a dab of hot glue once you've got it dialed in again...
 
The manufacturer hot glued the lens cylinder to the housing. Looks incredibly difficult to remove without damaging, but maybe I could lightly heat it up. Perhaps, I don't need to touch that part, maybe it was my re-assembly issue. But let me focus on one issue at a time. I want to try to fix the IR cut filter.

So if I force this camera to ALWAYS be in color and never use infrared, in theory, could I force the filter cut to always be on?
 
Do you guys know what voltage is needed to activate the IR filter from that itty bitty connector? I have some li-ion batteries @ 3.7v that I can wire up and try to juice it on the bench to see if it could work. I can also try the magnet method next but that may not be the same test.
 
yes, but that requires your filter mechanism to be working.
ie, it needs to be powered up during the day to keep the filter in place.

alternative for permanent color use might be to apply a small full-time filter to the back of the lens...
 
fileter mechanism might work on 3.3 - 5v. 3.7v might not be enuf, but safe to try.

5v certainly won't hurt it. probably even ok to test with 12V, but only briefly if not sure...
 
Results are in guys. So here's the problem!

Right off the bat, the filter is stuck in clear mode. When camera has no power or filter cut has no power.

When I juiced it with 3.7V from lithium-ion battery, immediately, it clicked and the blue filter popped out. When I remove the power, the filter cut does not return back to clear mode. So it stays in filtered mode. I tried reversing polarity but nothing happened.

I can manually switch the filter going back and forth easily but I feel like when sliding between filter and no filter, it has a "notchy" feeling like it wants to stay in place. There's definitely spring action, but the spring is not making it stay in clear mode. It feels like a toggle.

So is my understanding correct that IF I let it stay in the filtered mode (blue screen), forever, it will work for both day and night so long as I do not activate infrared light and go to black and white mode? Is my understanding correct?

On a side note, I fixed the focus problem as well!!! It was me not bolting the lens housing back to the image sensor PCB tight enough. The tighter I kept screwing it, the better the focus got!!

In this example video, my IR cut filter is NOT behaving like this:
Mine won't spring back to clear.


Thank you.
 
Last edited:
MakeItRain said:
I basically force the IR filter to stay in filter mode.
Click to expand...
Another option - should you feel inclined to spend more time on this - is simply to replace the lens mount with IRC with another one.

These are really cheap - loads of choice on eBay and Aliexpress.
The lens mounts are standardised, it's just a quick swap.
 
alastairstevenson said:
Another option - should you feel inclined to spend more time on this - is simply to replace the lens mount with IRC with another one.

These are really cheap - loads of choice on eBay and Aliexpress.
The lens mounts are standardised, it's just a quick swap.
Click to expand...

Could you elaborate on what a IRC is?
 
Are you sure they’re all universal? It looks to me like you have to find a very specific one that would fit the bullet can.
 
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