How do i add 9 volt ? - Page 1
Forum section: electronics / projects

author: JanJansen
author_rank: Frequent Contributor
timestamp: September 05, 2017, 04:11:16 pm
content: Hi, i wanto build a drummachine ( TR-808 ).It seems for the triggering i need a voltage between 9 and 14 volt.I have a voltage from 0 to 5 volt coming out the microcontroller DAC, buffered in a rail to rail opamp.How do i add 9 volt ?, so the range will be 9 to 14 volt instead of 0 to 5 volts.thanks in advance

author: Benta
author_rank: Super Contributor
timestamp: September 05, 2017, 04:16:11 pm
content: Place a 9 V battery in series with the wire?

author: JanJansen
author_rank: Frequent Contributor
timestamp: September 05, 2017, 04:25:02 pm
content: Very funny, i dont wanto ruin my expensive super fast rail to rail opamp.

author: Zero999
author_rank: Super Contributor
timestamp: September 05, 2017, 04:47:05 pm
content: Quote from: JanJansen on September 05, 2017, 04:25:02 pmIt sounds crazy but he wasn't far off. Obviously don't use a 9V battery. A voltage reference, such as the TL431, set to 9V, in series with the output, connected to a higher voltage, via a suitable pull-up resistor will do. You will not ruin the op-amp, if the current is limited to a safe level.See attached. R3 limits the current through the op-amp's output to just 6mA.

author: Benta
author_rank: Super Contributor
timestamp: September 05, 2017, 06:48:39 pm
content: Perhaps my joke wasn't that good, but you've misunderstood the Trigger Out specifications completely.The TR-808 Operation Manual states:"Each trigger signal is a positive, 15 Volt, 20 millisecond pulse..."I've no idea how you got to the 9...14 V trigger voltage.The trigger outputs should be 0/15 V. An open collector output with pullup to +15 V should do the job. 20 ms is slooooow.

author: Zero999
author_rank: Super Contributor
timestamp: September 05, 2017, 07:07:14 pm
content: I haven't read the manual.If all that's required is a digital pulse, when why the heck use an op-amp and DAC? It makes no sense. All that's needed is a digital logic level shifter.If the output is a fairly high impedance and the input can drive the current, a simple NPN transistor, in common base configuration will do. The schematic below will work when V1 = 15V. The low level can be limited by adding a resistor in series with V3.

author: Benta
author_rank: Super Contributor
timestamp: September 05, 2017, 08:01:45 pm
content: Actually, the nicest way of doing this is with a simple LED-BJT optocoupler. It protects the internal circuit when pulling and inserting connectors, and makes level-shifting very easy.The OP still needs a +15 V supply, though.

author: joshtyler
author_rank: Contributor
timestamp: September 05, 2017, 08:15:05 pm
content: OP, what are you trying to achieve? According to the manual, the trigger signals on the TR-808 areoutputs.Are you trying to design a machine that functions the same as the TR-808, or are you trying to interface with a TR-808?If it's the latter, what exactly are you trying to do with the trigger signals?

author: JanJansen
author_rank: Frequent Contributor
timestamp: September 06, 2017, 02:34:25 pm
content: Quote from: joshtyler on September 05, 2017, 08:15:05 pmI am trying to add velocity just like a TR909,normally the TR808 has only 2 volumes, accented notes, and no accent.I searched about the voltage coming into the PNP transistor in the trigger circuit, i readed online that the voltages are from 9 to 14 volt range.Normally i go from the 8 bit DAC into a rail to rail opamp, then to a 4051 ( on main board ) to sample it in a JFET with 100pf capacitor ( on individual voice board ),so normally i have a range from 1 to 6 volt for velocity with my custom drummachines.Take a look into this pdf schematic for the bass drum :http://www.ericarcher.net/wp-content/uploads/2014/07/tr-808-bass-drum-diy-project.pdfAt the ACCENT connection, there i want to have a voltage of 9 to 14 volt.btw : i am not using C14, D3 & R27 from this schematic, my microcontroller trigger pin goes into R1.The PDF says : the easiest way is to tie ACCENT to +12V (+15V), and connectthe logic signal to TRIGGER.I want it tied to a value that goes from a soft sound to the hardest sound.Quote from: Benta on September 05, 2017, 06:48:39 pmTransistors T3 & T6 make the 15 volt pulse from a MCU pin, the 15 volt is variable for accented notes or no accent, 15 volt ( or 14 like i readed ) is the max.If someone has a 808 to measure, can you please verify what the voltage is at the ACCENT connection ?Quote from: Hero999 on September 05, 2017, 04:47:05 pmSuch parts are new territory for me,as far as i see it as beginner : connect 5 volt to 15 volt with 1K resistor is short circuit.btw : i see they also used a opamp for the second voice board ( at connection J4 ).

author: little_grey
author_rank: Regular Contributor
timestamp: September 06, 2017, 02:47:13 pm
content: a little off topic, and possibly quite a noob-ish (if anyone still uses the term noob) question, but what are you using for your schematics/graphs?could be very useful for some future CAN projects

author: Yansi
author_rank: Super Contributor
timestamp: September 06, 2017, 02:52:00 pm
content: LTSpice?

author: Zero999
author_rank: Super Contributor
timestamp: September 06, 2017, 05:36:28 pm
content: Quote from: JanJansen on September 06, 2017, 02:34:25 pmThe TL431 is a fairly standard part. I used a non-standard symbol because LTSpice doesn't come with it built-in and didn't want to make a zip file with the symbol. Don't let that confuse you.A short circuit is when there is nothing to limit the current. In the circuit I posted, R3 limits the current to a safe level. V1 is a 15V power supply and V2 is the input voltage from the op-amp, which is converted to 9V to 14V.

author: JanJansen
author_rank: Frequent Contributor
timestamp: September 07, 2017, 02:27:11 pm
content: Suppose i need 8 to 14 volt then ?

author: WZOLL
author_rank: Regular Contributor
timestamp: September 07, 2017, 05:27:05 pm
content: http://www.ericarcher.net/wp-content/uploads/2014/07/tr-808-bass-drum-diy-project.pdfCheck this website for some help on how to trigger it. This circuit will trigger the drum circuit regardless of the pulse width.

author: Zero999
author_rank: Super Contributor
timestamp: September 07, 2017, 09:02:19 pm
content: Quote from: JanJansen on September 07, 2017, 02:27:11 pmFrom what? 0V to 5V? That would require some gain. A non-inverting op-amp circuit, with a gain of 1.2, could be used to get 0V to 6V before passing it to the TL431 circuit with its voltage set to 8V.Another option is to use an op-amp and a separate voltage reference, at the input. Check out the following application note:http://www.ti.com/lit/an/sloa097/sloa097.pdf

author: JanJansen
author_rank: Frequent Contributor
timestamp: September 08, 2017, 01:44:28 pm
content: Thanks you Hero, i like the idea of a opamp + resistors instead of special IC stuff.Figure 2. Schematic Diagram for Positive m and Negative bwith this i dont need a resistor on the 0-5 v range signal ( m )the offset can be inverted, nice.I have to try this.Anyways it seems i need a voltage of :4 to 14 voltand the other voltage :7 to 14 volt.Now i have 0 to 5 volt, how do i convert it to 4 to 14 volt and 7 to 14 volt ?thanks