Your use was OK too. Its in his specific idss list I preferred them in different positions since his stronger ones were significantly higher than the "3-5mA subgroup" mentioned in the guide. So his calculations will have the CCS Leds Vf closer to reality. The general instructions cater for reliability with the max Vout possible range also in mind. At this Vout level they are making no big difference for various TO-92 dissipations anyway.
Thanks Salas for the info.
So this my plan based on your 2SK117 input, for a mildly adjustable mosfet +/-26V @ 300mA for BA-3 FE:
Q102/202 = 5.77/5.77mA
Q103/203 = 4.00/4.33mA
Q105/205 = 3.11/3.12mA
And also these:
C105/205 = 10kuF/63V Chemi-Con SMH
C102/104/202/204 = 10uF MKS4 Wima
R101/201 = 10R/5W wirewound
R103/203 = 4.42k
R105/205 = 2k 3296Y
Open to suggestions if there's a more optimal configuration for this particular application!
BK
So this my plan based on your 2SK117 input, for a mildly adjustable mosfet +/-26V @ 300mA for BA-3 FE:
Q102/202 = 5.77/5.77mA
Q103/203 = 4.00/4.33mA
Q105/205 = 3.11/3.12mA
And also these:
C105/205 = 10kuF/63V Chemi-Con SMH
C102/104/202/204 = 10uF MKS4 Wima
R101/201 = 10R/5W wirewound
R103/203 = 4.42k
R105/205 = 2k 3296Y
Open to suggestions if there's a more optimal configuration for this particular application!
BK
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Make R103/203 5.6k to have bit more range just in case your max Vout with the trimmers will be at the short edge of max enough. Q103/203 will lose about 17% Idss from nominal when in this circuit.
10 Ohm R101/102 with four green Leds will not likely give 300mA CCS. About 220mA rather. Have 6.8R 3-5W also in hand. Because the Leds will not show nominal Vf in circuit. Nominal is usually stated at 20mA. Calculate greens with 1.95-2V Vf maybe. Reds around 1.8V.
10 Ohm R101/102 with four green Leds will not likely give 300mA CCS. About 220mA rather. Have 6.8R 3-5W also in hand. Because the Leds will not show nominal Vf in circuit. Nominal is usually stated at 20mA. Calculate greens with 1.95-2V Vf maybe. Reds around 1.8V.
Thanks again!
For R101/201, is Vishay RS series (3.75W/1%/50ppm) a good choice or is something else better for this location?
BTW, LEDs are from TeaBag's kits a couple of years (?) back.
BK
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Yes very good resistor,i use it in Reflektor D,much better than Mills resistor.
Ayrton-Perry 50ppm wirewound as those are they should be an excellent choice
Do the Leds look like these? http://gr.mouser.com/Search/Refine.aspx?Keyword=wp2773
Great - R101/201 now locked in for both 6.8R and 10R.
Yes, the non-standard shape of the LEDs matches those in your link.
BK
One more question here. On the Vishay RS part linked in my post - do I need the "NS" non-inductive type? The datasheet suggests (?) only those are Ayrton-Perry type. I have to admit ignorance on this topic...
BK
Expect those Leds roughly 1.84 and 1.97 Vf (red-green) @ 3mA which is more appropriate for in circuit calculations with that excel
Yes the "NS", they are big enough size parts though, consider that fact. 10R I don't see in NS powerful enough stocked at Mouser's. Only 6.8R at 5W.
Manufacturer Part No:
NS0056R800FE12
Thanks for all the great input!
This is the ohmite 10R I was originally planning on for R101. Would seem to fit well and it's non-inductive.
The Caddock MP930 looks terrific, but the LS is 5mm and the board is 19mm. Just bend the leads?
Below is my excel calc with specific inputs (-17% for Q103). Seem OK? I'm expecting/hoping top bump Vout to maybe 28-30V later if the SQ benefits.
BK
Attachments
I built my first sslv today and ran into some troubles. I am quite inexperienced and would be very grateful for some advice.
After my first power up all LEDs went on and everything looked good. The problem is, I was aiming for 10 V and my output voltage is 5v. My ac in is 12v. I used the excel spreadsheet to calculate R103 and R105. I used 1,5k for R103 and a 1k trimpot. The problem is, adjusting the trimpot does not change my output voltage at all.
Do you have any ideas where i could have gone wrong? my only idea is the trimpot ... just to be sure - a/the trimpot is not directional, right? (used the suggested 3296Y bourns one) mounted it like pictured on the pcb, but after looking at the "pinout" i realized its the wrong way (leg one and three switched)
After my first power up all LEDs went on and everything looked good. The problem is, I was aiming for 10 V and my output voltage is 5v. My ac in is 12v. I used the excel spreadsheet to calculate R103 and R105. I used 1,5k for R103 and a 1k trimpot. The problem is, adjusting the trimpot does not change my output voltage at all.
Do you have any ideas where i could have gone wrong? my only idea is the trimpot ... just to be sure - a/the trimpot is not directional, right? (used the suggested 3296Y bourns one) mounted it like pictured on the pcb, but after looking at the "pinout" i realized its the wrong way (leg one and three switched)
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Um... I used the 20r resistor from the ref-d Set that teabag supplies... I think that should be fine?...
That one would demand half an Ampere to reach 10V and some spare for the regulator to feed itself. If your CCS is set at about 250mA it would limit at 5V. What you want to do is to project for your real load consumption. If you know it will be 100mA at 10V for instance you put 100 Ohm dummy load. That way you not only do the voltage setting but you also know how the sinks will heat up when in the actual duty.
