Benboost PHR-805T

[nellywhads]

Hey everyone,

I'm working on a PHR-805T build in a 14500 host drivin with a benboost set to 190mA (if anyone suggests i run a lower current - please help me choose a resistor for it?).

I have recently realized that the benboost isn't very good with host-negative current regulation, while the PHR-805T diode is case negative. So my question is as follows:

Can I simply isolate my heatsink from the host (ie. black electrical tape), which will also isolate the diode and the benboost, but still leave the negative of my 14500 battery running through the host (from the clicky switch at the back end)?

If this isn't possible, can anyone suggest another take on this build? I've already ordered parts, but really I just wanna make it work

EDIT:

Found a resistor combo to get the benboost running at 100mA's - now I'm just asking about isolation the case negative diode


EDIT: Adding Pictures

Basic host parts - Clicky end cap with spring for battery negative, battery tube, head

Original flashlight electronic assembly

Assembled electronics (Ignore the cheap calipers - my good ones are in my room at school), comes to exacly 25mm when measured with the real ones too

Custom lathed heat sink (OD ~17mm, ID ~12mm, length ~24mm (left 1mm for the battery contact board at the end)

As described above (The contact board is a litle worn but I'll touch it up before putting it all together)

Host head (ID ~17mm, <0.5mm clearance against the host) - it IS anodized

Battery tube (with just an AA in there) and the host head + heatsink + battery contact board. You can see the manufacturer has grinded off the anodized edge on the battery tube to make contact with the board in the head

Thanks,
Nelly

 

[ARG]

On mobile, so I can't look at datasheets to figure out a new resistor value for you, but 190mA will definitely fry your diode.

 

[nellywhads]

Really? I thought the PHR's could take upto 250 before frying...

Do PM me with some resistor options though if you don't mind - if it saves the diode then I'm in

On mobile, so I can't look at datasheets to figure out a new resistor value for you, but 190mA will definitely fry your diode.

 

[Polonium210]

On PHR's I wouldn't push it past 125mA

 

[nellywhads]

FOund out how to run the Benboost at 100mA - so ever with a spike in current I'll be covered.

Now, how do I isolate the diode for safe operation?

 

[grainde]

Thermal epoxy would be the best option, but test first with a DMM to make sure it is electrically Isolated! Arctic alumina is a good choice.:beer:

Edit: an anodised heat sink is also a possibility esp. when used in conjunction with thermal epoxy.

 

[nellywhads]

Thermal epoxy would be the best option, but test first with a DMM to make sure it is electrically Isolated! Arctic alumina is a good choice.:beer:

Edit: an anodised heat sink is also a possibility esp. when used in conjunction with thermal epoxy.

Should I apply the alumina between the diode housing (Aixiz) and the copper heat sink? Or between the copper heatsink and the host? (The heat sink has an OD of 17mm and is around 25mm long...that's a lot of thermal epoxy )

 

[grainde]

To be honest unless its a really bad fit, you wont use much epoxy. If the heat sink is very loose the thermal epoxy wont help much either and you could probably go the tape route. Is the inside of the host anodised? I use thermal grease between the diode and module and module heatsink as this had better thermal properties. To electrically isolate epoxy is better and once set up nothing can move to create a short.:beer:

 

[nellywhads]

Hmm, I think I'll go the epoxy between the module and the heatsink route. The heatsink is actually a pretty decent fit (<0.5mm wiggle room). The inside of the host is anodidised but if I keep the copper heatsink free inside the host then I could potentially create a hot-swappable laser module (driver and all) for this host

I'll post some pics in a few mins to give everyone an idea. As to what I'm going for.

To be honest unless its a really bad fit, you wont use much epoxy. If the heat sink is very loose the thermal epoxy wont help much either and you could probably go the tape route. Is the inside of the host anodised? I use thermal grease between the diode and module and module heatsink as this had better thermal properties. To electrically isolate epoxy is better and once set up nothing can move to create a short.:beer:

 

[nellywhads]

OP edited with pics of assembly

 

[nellywhads]

BUMP + Question:

Can anyone help me out with how many diodes to use in a test load for a PHR 805? I'm building a variable test load but I've heard debate between 4-6 diodes - how many should I be using when testing my driver?

Thanks guys,
Nelly

 

[Polonium210]

Use 6 x 1N4007 diodes :beer:

 

[nellywhads]

Can I Use 6 1N5004's? (They're part of the DIY Test load I'm making)

Use 6 x 1N4007 diodes :beer:

 

[The Lightning Stalker]

Yes, those will work. (I think you mean
1N5404.) I would go with 9 of them in
series just because the current is so low.

 

[nellywhads]

Thanks - will do

On the benboost mini's - would I need any heatsinking at this curent? I don't think I will but I just wanna be sure...

Yes, those will work. (I think you mean
1N5404.) I would go with 9 of them in
series just because the current is so low.

 

[o_DEATH_ANG3L_o]

I ran a PHR-805T at 100 mA and it is still running strong to this day from 4 years ago. Highly doubt you will need to heatsink your driver. But if you feel it will help or give you peace of mind then by all means sink it.