1050 Bi-Colour LED Resistors

[+Nezgar]

OK folks, I thought this would be easy, but I need some basic electronics support to figure out the resistors I need... I want to replace the stock red power LED with a Red/Green bi-colour LED that changes along with a write-protect DPST switch (On-On / 6 terminal) with a base 5V from the drive.

They are just generic LED's from eBay/china so I have to guess the specs, but common voltages seem to be ~2-2.6V for red, and 2.1-3V for green, 20-30mA forward current.

I tried calculating, using 120ohms to get 5V --> 2.6V for Green, and 150ohms for 5V --> 2V for Red... Something is off because I burned out a few when testing... (too high voltage) Then I noticed the local shop sold me 1/2W resistors, maybe should be 1/4W resistors?

 

Thanks in advance.

[Level42]

The wattage doesn't matter at all, they still have the same resistance. A higher wattage only enables the resistor to handle more current, which is absolutely NO factor when it comes to LEDs (They use very little current.)

 

You can always try to start with a larger resistor like 680 ohms, see what happens, then go down in value step by step. I

 

However, those resistor values you mention do seem about right for regular LEDs at 5V...maybe there's something else wrong ?

[+Nezgar]

Looks like I have to recalculate, I forgot the seller listed the specs in the ebay description... Looks like I burned out the red on one of these, but the green is still OK.

 

Reran the calculations for the resistors I have...

120ohm = 5V-->2.6V, which is too high for Red (Zappo) and too low for Green

150ohm = 5V-->2V, should be OK for Red

 

Looks like I need to buy 100ohm for 5V-->3.0V?

[+tf_hh]

Looks like I have to recalculate, I forgot the seller listed the specs in the ebay description... Looks like I burned out the red on one of these, but the green is still OK.

Looks like I need to buy 100ohm for 5V-->3.0V?

 

Don´t make it so complicated

 

The values provided by the LED manufacturer are MAX values you should "offer" the LED to consume. Most LEDs are lighting up with much less power. I use something around 220...400 Ohms for 5V voltage and LEDs of any kind. It´s enough to make them light up and also enough limitation to keep the LED from consuming too much power.

 

When you want to use it for a write protect switch, take a dual color LED with common anode and connect the common anode using one resistor of 220...400 ohms to +5V. The both cathodes can be used with a DPST switch - one position of the switch (where the RED side is for example) is connected in parallel to pin 2 or 3 of the 74LS02 chip. This NOR gate (it´s output) is connected to WPRT of the FDC. By default (no connection is made) the resistor R51 (20k) keeps the floating input at high level - what´s LOW after the NOR gate - disk writing is denied. When you set this input to low by the switch, writing is allowed. This way needs only 3 wires, no other chips, no complicated stuff.

[_The Doctor__]

so regular red power led is normal... power led turns orange.. (red and green at same time) is overide to write protect always, and power led just green would be overide to no protection always..?

or would orange be normal operation, red is always protected and green is never protected...

 

same thing on an XF but green is normal orange is no protection, and red is always protected... perhaps?

 

give the color choices some thought... oh no what about an rgb led? hmmmm sounds good....

Edited September 5, 2018 by _The Doctor__

[1050]

Figure for amperage and not voltage. Voltage will be

dependent on the LED type alone but amperage is the

only rope that works to tie this horse up with.

 

5 volts divided by 20 MA is 200 ohms if you want a bright

LED. As Turgen suggests they will work at much less

than maximum output and still be quite visible too.

 

Different colors are often not matched in perceived

brightness so you might want the stronger red at

8 MA and the green at 15 before they appear to be

the same strength.

[Mathy]

Hello guys

 

I'd use red for no protection, green for "no writing allowed" and orange for "normal". The color green is usually associated with "it's save", while red is often associated with danger.

 

Sincerely

 

Mathy

[+Nezgar]

Thanks all, I think I got it figured. I don't quite get the math, but I wired up some tests and have a working switch toggling between red & green without blowing up the LED now

 

Also was confused for a little about the polarity, I now know these are 'Common Anode' 3 pin LEDs, so + goes to either of the outer pins (determining colour) instead of the centre pin... So simplest is to use 1 resistor on the - pin, if brightness difference is OK. (or different resistors on each outer pin if different resistance wanted for each colour)

 

Since all I have is 120 and 150 ohm's right now, using 3x150ohm (=450) in series seems to be an acceptable brightness for both colours, and I measured it operating at 1.93V for red, 2.11V for green. So I shoudl get a single 470ohm resistor which would be much nicer. I should just get one of those cheap kits with many types.

 

My current goal is simply a WP on / WP off toggle, without the 'maybe' yellow mode, just disconnecting the photodiode entirely. I have Jurgen's switch method working so far connected to pin 2/3/4 to one side of the DPST switch, so this light will match that nicely.

 

Later on I might try to see how to make the Red/Yellow/Green switch. I think a relay is needed to make it work with a DPST on/off/on switch.

[1050]

Also was confused for a little about the polarity, I now know these are 'Common Anode' 3 pin LEDs, so + goes to either of the outer pins (determining colour) instead of the centre pin... So simplest is to use 1 resistor on the - pin, if brightness difference is OK. (or different resistors on each outer pin if different resistance wanted for each colour)

Still confused? Anode is positive, Cathode is negative.

[+Nezgar]

Hah apparently! so, it was single common cathode, 2 anodes.

[BillC]

I installed a write protect switch, with status monitored by red/green LEDs, in a 1050 over 30 years ago, now that I have more electronics knowledge and schematics, I see a simpler method than I used back then.

 

Remove JP7 and connect a SDPT center off switch as shown is the schematic below. When in first position it acts just like JP7(connecting to the sensor on the mechanism), off in the center(pulled high by R51), or to ground in the last position.

 

The high/low signal is inverted by a gate in U11 and becomes "N WPRT". Since we have a signal and inverted signal we can use these as connections for LEDs, The output of U11 can't deliver enough current to light an LED, but is rated to sink 16mA which should be sufficient, just a slightly higher value resistor/dimmer LED. This means connecting the LED anodes to VCC and the cathodes to the write protect circuit as shown. I used red/green for the LED connections, these may be reversed from what is desired.

 

The schematic below only shows the power supply circuitry, and the write protection circuitry, with my switch/LED modifications. The LEDs are shown as 2 separate ones, these could be combined in a single common anode LED. In the schematic I didn't remove the power LED, but there is no need for it if using 2 colors for write protection ON/OFF status.

 

Edited September 11, 2018 by BillC

[+Nezgar]

Much appreciated everyone. Schematics are still a bit too much for me, but interesting to analyze and learning slowly! Finally got back to messing with this again this evening.

 

Am I reading the schematic correctly that the J11 Pin 1 +5V already has a 150ohm resistor on it? so effectively I have 300ohm once I add my 150ohm as well?

 

I was able to start with just a simple DPST switch (2-position, 3 terminal on-on), which either connected J11 Pin 1 to 3 for write allow, or pin 2 to 3 for write protect. Simple enough, and worked well with no soldering to the 1050 PCB by using jumper wires to push onto the J11 pins. (No LED yet)

 

Then for the 2-colour LED, I figured there was already +5V and GND available on the switch, so why pull it from elsewhere? I was able to do it using no additional wires to the 1050 PCB, just the existing 3 from J11. Using a DPDT switch (2 position, 6 terminal on-on) I took the +5V from J11 Pin 1 from the terminal of the 1st/left 'side' of the switch through a 150ohm resistor to the centre terminal of the 2nd/right 'side' of the switch, and then connected the red & green anodes of the LED to the top and bottom terminals. Then the cathode was connected back to the bottom terminal of the 1st/left side of the switch (Connected to J11, Pin 2, GND).

 

I like that this requires no soldering to the 1050 PCB using these jumper wires. I drew this diagram to make it more clear in a non-schematic sort of way. My intent is to replace the power LED with this though, so I guess there is going to be some (de)soldering done on the PCB.

[_The Doctor__]

I think we wanted 3 modes of operation...

 

1. normal

2. always protected

3. always unprotected

 

and a color for each...

[BillC]

I think we wanted 3 modes of operation...

 

1. normal

2. always protected

3. always unprotected

 

and a color for each...

My schematic in post 11 does this, the write protect status is determined by whether the input to the gate of U11 is high or low, I measured 0.16V for write enabled and +4.98V for disabled, with the output of U11(inverted input) connected to the FDC.

 

When the transmitter/receiver are blocked by an un-notched disk the input of U11 is pulled to +5V by R51 disabling writing. When the transmitter/receiver aren't blocked, when the disk is notched, the receiver grounds the input of U11 to enable writing.

 

With J11 removed and the switch connected to its pads, the write protection operates as normal when the switch connects those pads, when the switch is in the center off position the input of U11 is pulled high by R51(write disabled), in the third position the switch connects the input of U11 to ground(write enabled).

 

A common anode(+) LED connected as shown to the input and output of the U11 gate will light one color or the other depending on the write protect status. I used a common anode LED since the 74LS02 is unable to supply enough current at high output, which prevents using a common cathode(-) LED, but can sink up to 16mA at low output.

 

@_The_Doctor__

Sorry, I thought you were responding to me, realized afterwards it was to Nezgar.

Edited September 16, 2018 by BillC

[_The Doctor__]

Correct I was talking to nezgar,

 

then I re visit your post for a second look and while I understood it, I caught these thoughts

 

I see sdpt and it didn't register in my foggy brain... SPDT co(center off)... I just saw it as SPDT (which is what it is)

and the other thing I didn't register in my brain was the switch symbol in the schematic having the lever on one side or the other instead of in the center off position.

 

I got it as connected as usual to sensor(low or high), tied to ground, or switch is open so high input.

 

It would be good to un jumble the switch and make the symbol for center off of the modern variety.

 

I like the mod. in that neither led will be on at the same time as the other...

the switch will always force the one led on the other off depending on position...

normal position will light one led or the other to show disk notch on or off as well...

 

don't have to pull disk to check notch which is very cool !!

We get real time protect status..

Edited September 16, 2018 by _The Doctor__

[BillC]

@_The_Doctor__

 

I only used Windows Paint to add my modifications, I just copied the format used for the power switch, adding the extra contact to make it SDPT. While I didn't show the center off position, I did list it in the text description.

 

It can be implemented with 2 separate LEDs, using the common anode bi-color LED allows it to replace the power LED if desired.

[_The Doctor__]

lol I had to reboot windows, I couldn't edit anything in a timely fashion and It kept messing up my post...

 

the unlabeled resistor to ground and on the led lines... what might the ballpark be on those.

 

I was hoping to put the common bicolor in the power led hole of the 1050 or maybe light up the far side of the drive slot with it.

The other thing I was hoping for is to have both the power and the write protect switch in the same hole using slim switches..

Edited September 16, 2018 by _The Doctor__

[BillC]

lol I had to reboot windows, I couldn't edit anything in a timely fashion and It kept messing up my post...

 

the unlabeled resistor to ground and on the led lines... what might the ballpark be on those.

 

I was hoping to put the common bicolor in the power led hole of the 1050 or maybe light up the far side of the drive slot with it.

The other thing I was hoping for is to have both the power and the write protect switch in the same hole using slim switches..

The LED between the switch and ground isn't really necessary, I put it there so that the write enabled LED could be adjusted to the same current(intensity) when enabled in both end switch positions, would be a slight difference due to the the +0.16V low value on the mechanism sensor.

 

The power LED uses an 180 ohm resistor(R70), simply connecting to the power LEDs anode connection leaves this resistor in circuit and may be all that's required. I showed separate resistors because red is usually brighter than green.

 

Below is a simplified schematic, updating the switch and removing the power supply circuit.

 

[BillC]

The other thing I was hoping for is to have both the power and the write protect switch in the same hole using slim switches..

I think it would be possible to install 2 vertical toggle switches in place of the current rocker switch. A short lever SPST or SPDT(2nd pole unused like current switch) on the left for power, and a long lever SPDT-CO to the right for write protection.

 

The short lever on the power switch would make it harder to accidentally turn power off when using the write protect switch.

 

I was basing this on the size of the SPDT vertical switches in the attached PDF.

100A-1.pdf

Edited September 20, 2018 by BillC

[BillC]

I believe I found a good SPDT-CO toggle switch(2 actually) with a red/green LED in the handle for installing as a write protect switch in place of the power LED, no need to modify the power switch. The LED hole in the faceplate would need to be modified, but nothing else externally. The red/green LED is common anode and independant of the switch, 3 terminals for each.

 

These are the NKK B13JJVCF/B13JJHCF, currently listed for $8.23 at Digikey. They currently have 48 of the first, none of the second. The only difference between them is the direction the toggle operates and the PCB footprint of the pins.

 

https://www.digikey.com/product-detail/en/nkk-switches/B13JJVCF/B13JJVCF-ND/2103909

https://www.digikey.com/product-detail/en/nkk-switches/B13JJHCF/B13JJHCF-ND/2103907

Edited September 20, 2018 by BillC

[BillC]

I checked the specification sheet for the switches listed in my previous post and they will fit in place of the power LED, and provide write protect switching and red/green status LEDs.

 

Below is an image showing its approximate footprint on the 1050 PCB, the rear pad locations for the vertical switch version are touching the pads for the power LED. The image has the solder pads for both the vertical and horizontal versions. The vertical version doesn't use the 2 pads on the center line, the horizontal version doesn't use the 2 pads furthest back.

 

Edited September 23, 2018 by BillC

[_The Doctor__]

Nailed it! Good work, they should have rolled off the line like that!

[BillC]

The B series switch LEDs have higher forward voltage than the original power LED.

The forward voltage for the red LED is 1.95V, which means the current limiting resistor will need to reduce the voltage by 3.05V at the desired current.

The forward voltage for the green LED is 3.3V, which means the current limiting resistor will need to reduce the voltage by 1.7V at the desired current.

 

The 74LS02 is rated at a maximum low output current of 16mA, if higher current is desired for the write protection ON LED there is an unused gate on U11 that could be connected in parallel to double the maximum current. The image below is from the SAMS Computerfacts 1050 Manual, with the unused gate highlighted.

Edited September 24, 2018 by BillC

[_The Doctor__]

yeah they want about 20ma on the newer ones, for both red and green alike...for normal brightness...

I see they list for amber as well.... 2v.... shooting down the middle.... red and green on at same time but still about the same milli amps... i forgot right after I closed the sheet...

Edited September 24, 2018 by _The Doctor__

[BillC]

Here is an updated image of the write protect circuit from the SAMS Computerfacts1050 schematic, showing the connections for the B13JJVCF as write protect switch/status LED, along with adding the unused gate of U11 to allow increased current for the red LED.

 

I chose the down position of the switch for the NORMAL(mechanism sensor) operation as this switch then matches the positions used by the Happy Controller write protection switch.

Edited September 24, 2018 by BillC